I live in Japan and last year when we moved from an apartment to a house we installed a Mitsubishi EcoCute heat pump water heater which already has these features and is also a CO2 heat pump.
We have one of the "all-denka" electric plans, where we trade off cheap rates during solar hours for expensive rates during duck curve hours. By having the hot water only run during cheap hours, and having the aircon turned off/down during the expensive hours, we're paying less in energy for our all-electric house than we did in combined electric+gas in our 3x smaller apartment.
We pay approx (before fees, and the rates change slightly by season):
* 8 AM - 10 AM: 35 yen/kWh
* 10 AM - 4 PM: 13 yen/kWh
* 4 PM - 6 PM: 35 yen/kWh
* 6 PM - 8 AM: 19 yen/kWh
Our Mitsubishi has other nice features like it can recirculate the water in the bath through a heat exchanger after you already filled it and got in, so it will keep the water from cooling down to lukewarm, and you can even adjust the bath water temperature if you ended up with filling it with too warm or too cold water. Of course, there's also an app so you can start filling up the bathtub when you leave work for home so a hot bath is waiting for you. There's also an intercom to the kitchen "so mom can tell the kids to get out of the bath, dinner is ready".
edit: the wifi integration does have one actually useful feature: if we had solar panels, then it can use data from them to know when to run "for free", and it can use weather data to predict if it should wait for sun or not to run
> Our Mitsubishi has other nice features like it can recirculate the water in the bath through a heat exchanger after you already filled it and got in, so it will keep the water from cooling down to lukewarm, and you can even adjust the bath water temperature if you ended up with filling it with too warm or too cold water.
How long do you sit in a bath?
> Of course, there's also an app so you can start filling up the bathtub when you leave work for home so a hot bath is waiting for you.
My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
Another Japan resident here! It is common for a family to share a bath for the evening. (One at a time!) This works because each person showers to get clean before you get in the bath. Many also have folding bath covers, which help to avoid the water from cooling down and to keep the water clean during the showers. Still, nobody wants to be last.
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
A smart reaction! But most baths are also whole-room units, with a floor drain, and are intended to get wet. I myself have forgotten to stop the bath water a number of times (neither I nor my bath are so "smart") and while it is an unfortunate waste of water, there is no danger of flooding, only slight embarrassment.
In most ways, yes. E.g. you clean yourself before you get in, so the water remains relatively clean after a few people. Unlike a hot tub though it's drained between uses, so it doesn't really have some of the nastier issues that hot tubs can acquire (nor does it need higher chlorine content to mitigate it).
80kg of meat can hold a lot of heat. It cools quicker than you think it would. Also, Japanese families often share the bathwater within themselves(but everyone showers outside the tub first), and the water will become lukewarm at some point in that use case.
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
Yep, remotely operating a machinery will always have some risks. Every machinery should have someone with an emergency stop button should be monitoring it at all time, ideally. But it's a well engineered tub auto-fill in the shower room, it effectively belongs to "inherently safe" category of equipment.
All my tubs and sinks in the bathrooms have an 'overflow drain' near the top which you are unable to fill beyond. Is there any reason why that wouldn't be sufficient?
Yeah, if the drain in the sink is clogged. US bathroom pipe is 1.25" which will (probably) lead to a 2" and 4" pipe eventually (depending on when, where, and how your house was built ofc). The hole in the sink leads to the same initial pipe.
In the US, any tub made past about 1900 or so has an overflow drain that prevents overfilling. The adoption of such drains not quite contemporaneous with the adoption of indoor plumbing, but very soon after.
It's the metal plate usually just below the faucet that looks like it might be useless. But it has an opening underneath to let the overflow water in. These are always sized to handle more water than the faucet can output.
This is basically a non-concern in anything but very, very old, unremodeled bathrooms.
My last apartment had the overflow drain hole but it wasn't attached to anything. The water just went directly into the wooden cabinet underneath. Madness. Literally worse than not having the hole because it reduced the capacity of the sink. This is what happens when landlords who DGAF hire handymen who DGAF to do all the work on their units.
The tub sits in a big shower booth. Other bathroom amenities like sink and washing machines are installed outside the booth. Toilet is usually a separate room entirely. So no problem overflowing water onto the floor since that's how you take a shower.
I'm an American and my answer is at least an hour, maybe more, depending on how I'm feeling. I usually listen to an audiobook. Baths are for hanging out and relaxing in.
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
I forgot to mention that it senses and automatically stops filling the bath at a select number of liters, even if you start a bath using the physical button when you're at home.
If I'm in the bath I'm either reading a good book, or talking with my wife (I have a tub big enough for two - takes a lot of water to fill) - either way I'm going to be in it for an hour or two. As the other poster said, if I want to get clean I'll take a quick shower. The tub is nice when my muscles get sore and tight from work.
This was my biggest takeaway from Japan in terms of home design - the bathroom design. At a small apartment in Tokyo the "bathroom" was in fact three separate spaces: a nook where the washer and sink lived which opened into the living room, one side of the nook featured the toilet closet, the other, and actual bathroom with tub and shower. This lets three people use the plumbing fixtures - toilet, shower/bath and sink. Though not all of the places I stayed at split the sink and bathroom.
Contrast this with the all-in-one design where a person taking a shower monopolizes all the plumbing fixtures even while they are not using them. I was on a bachelor party trip with 8 guys and two bathrooms where some inconsiderate people camped out in the shower for 20 minutes while people waking up had to pee so badly they went outside in the bushes. Meanwhile on a trip to Japan with five people we could easily share one or two split bathrooms and never had an issue.
Oh, and the electric bidet is a clear winner in terms of bathroom accessory to buy. Less TP use and no threat of swamp ass that demands you take a shower. Heated seat in winter is a blessing, especially in the morning. After my Japan trip it was the first thing I bought when I got back home.
Interesting that that's a feature of the water heater and not the tub. It has to travel through the plumbing all the way round-trip to the heater? You must have isolated recirculation plumbing to deal with the grey water, yeah?
Typically Japanese homes are laid out economically so the bath is right where the hot water heater is. In our house from the 70's it's probably not more than meter through the wall to the water heater. Even in apartment buildings, typically each apartment has it's own tankless gas water heater on the outside wall of the building so it's easy to meter usage separately.
Technically, you could also just pull refrigerant lines from the heat pump to the bath tub - you probably already run those to the indoor AC units you have in different rooms anyway - or connect the bath tub to the hot water lines you run to the radiators. Both imply a grey water heat exchanger built into the tub.
Depends on setup, of course. If there's a central AC blowing hot/cold air through ducts, you're stuck using a grey water loop. But it is the least attractive setup...
Barring some catastrophic overflow clogging + drain clogging or other issue, your house will be fine! Your wallet may not be.
These are truly _bath_ rooms. The shower and bath are side by side, with the intent that you wash off before hopping into the bath to soak. Thus if the tub overflowed it would just go down the shower drain.
Anyone who has used a nice Japanese toilet knows the US is behind in terms of bathroom tech, but personally I'm glad that nothing my bathroom is controlled by app and that I don't have to spend my time worrying about what time of day it is when I want hot water or air conditioning. I hope my power company never decides to start with "surge pricing" so they can hike up my rates any time it's too hot or cold outside.
Solar + batteries is cheaper than ever. Americans are often full preppers and DIY but when we speak about energy autonomy and efficiency they immediately get some weird allergy.
Japan has no domestic source of oil or natural gas. The US has so much natural gas that it’s flared off to the atmosphere in some places. Natural gas is insanely cheap to heat with as a result and condensing boilers are extremely efficient. This created a scenario where heat pumps may be more efficient, but they might still cost more to operate. The raw cost of gas excluding pipeline and connection costs in my state is $0.57 for what is equivalent to 29.3kW of electricity. It’s very hard to beat that if you have a 98% efficient boiler, even with a COP of 4 if you’re paying $0.15/kWh, that means the equivalent amount of heat moved would cost 0.15*7=$1.05 or just under twice as expensive.
Yep - where I am, it's moderately more expensive to use our heat pump to heat the house (at basically any time of year) than to use the gas furnace, and approximately nobody has a heat pump water heater. And with datacenters trying to move in, that equation may get even worse in the future. Gas is surprisingly, weirdly cheap, often not even metered in apartments.
Having two options during cold winters can pay for itself with one emergency repair though, or be a massive savings if it can't be fixed fast enough and pipes burst.
How does cleaning of the heat exchanger work? From my experience with Jaccuzzi-style baths anything that recirculates bathwater gets very nasty very quick and is a nightmare to clean.
in Japan you tend to shower & wash yourself clean _before_ getting into any bath. In the west people don't do it or do it very half asset. And tbh. a lot of places have combined bath/shower so you kinda can't even do it Japanese style nicely.
That alone probably will make a huge difference in how often you have to deep clean it.
> Our Mitsubishi has other nice features like it can recirculate the water in the bath through a heat exchanger after you already filled it and got in, so it will keep the water from cooling down to lukewarm
I've also got the ecocute but I was told that it's cheaper to just pump fresh hot water into the bath than recirculate the cooled down water. It uses less energy to pump the already boiled water into the tub than to heat it back up.
I don't see how that is possible. Either way you need the same amount of heat added to the tub. Maybe you save a little because the return pipes are not cooling the water, but otherwise the needed heat should be the same. I personally insulated all my hot water pipes which solves that worry.
Though fresh water and letting out the old will clean the water you are soaking in, which may be valuable.
The way ecocute works is that it heats water at times when electricity is cheap and stores it in a highly insulated tank. So if you’re having a soak in the evening, it’s cheaper to use the water that is already preheated at cheaper rates and stored, than to reheat it again using the expensive to peak time rates.
My rates are 36yen from 6am to 10pm and 19yen on the other end.
Re-reading my earlier post, I should’ve said cost and not energy.
In the UK we've had off peak power overnight for decades. My current one is something like 1/3rd of the price of daytime power between 2300 and 0700.
However this is somewhat old fashioned, the most modern tarrifs vary on a 30 minute window, with prices set a day ahead. If there's a lot of solar and little demand on say a sunny sunday afternoon or windy february nighttime, then the prices may even go negative.
You want your consumption to be tied into there. You can do this with batteries -- for example on Tuesday I used 34kWh, 24kWh overnight (mainly to charge the car) and 10kWh in the day. If I had a battery I could have charged that battery overnight and saved a couple of quid, or about £600 a year (depends on what my daytime usage is)
However with a 30kWh battery I could have charged it on Sunday afternoon and been paid for that, and not used any power on Monday, Tuesday or Wednesday for the house. But then the agile rate last night was 25p/kWh. I did look at getting a battery and inverter installed but it wasn't cheap.
On top of that you've got self generation. I have very little solar generation, but in theory I reckon I could have 8kWp on the roof -- I'd want to charge the car (and house battery, and any heatpump or ac) when the sun was shining then, which would be even cheaper than charging at night. Home Assistant will do that, but it feels a little fragile with my car charger (if the HA dies, the charger won't start, and then I can't go anywhere. It's not a great charger)
Economy 7 and storage heaters. Heat up bricks overnight using cheap rate electricity so they can keep your home warm during the day while you’re out working.
In fairness it probably works ok for homes insulated to a much higher standard than most British ones.
Holy crap that re-circulation feature is luxurious!
I'd love to have something like that!
Whenever I take a hot shower I fantasize about putting in a liquid-to-liquid heat exchanger so the hot water can heat up the cold water and you can run the hot water at a much lower temperature.
This application with the bath tub feels way more justified.
That does exist. Simple versions just have a large, deep drain with coils the cold water runs through. Fancier ones have a proper heat exchanger next to the shower (requires a pump) or in the basement. Water sanitation rules probably make it non trivial to get a design certified.
Many people have thought about the drain heat exchanger. However drains need to be way oversized for various reasons and so you can't get good contact with the water: it is mostly air in the drain pipes.
> Some Japanese utilities have introduced tariffs designed to encourage daytime water heating as growing volumes of solar generation enter the grid. [Emphasis added.]
I was quite confused at the use of "tariff" here, as it meant to me a "tax on a good crossing a political boundary." Turns out, 'tariff' has an older meaning: a published schedule of fees or taxes issued by some authority.
I've read that the word is borrowed from Arabic, meaning notification, and I think at first it was price notifications and then people started using it to mean that the prices were bound to some schedule or condition.
For example in Turkish, "tarife" means only that: Conditional / Schedule-based pricing, and according to Sevan Nişanyan (a language researcher), Turkish borrowed it from Italian, where it was being used similarly. Import tariffs are a completely different word.
It apparently came to English through Italian -> Spanish -> French.
So I'm not a native English speaker but as far as I understand, import tariffs are just one kind of tariff.
From French, tarif, a table showing the amounts of payable fees, or a list of prices set for certain goods or services (1572), via Spanish tarifa, from Arabic ta'arifa, meaning notification, coming from 'arrifa, to let know.
Big fan of Etymology as well, mostly because my brain seemingly needs to understand the origin/history of terms to feel like I've fully grasped concepts.
US utilities also have Tariffs. It’s the statement of how the utility operates and charges users for service.
Anytime a utility needs to adjust costs/rates, they need to file a Rate Case with the public utility commissions, and resulting in changes to the Tariff.
My electricity contract in the Netherlands here is on a "Dynamisch tarief", with the most direct translation being "Dynamic tariff". It means I pay/get a different price for my power every 15 minutes.
"Tarief" just means price of mainly a service.
I think 'dynamic rate' is the proper translation for the US?
In the UK you can get agile tarrifs now where the price changes through the day according to demand and supply predictions. There's an API you can use to control chargers, heaters, bitcoin miners etc.
It's an arab loan word for ~"price list" (originally strongly suggesting an import-duty-like meaning).
The same word exists in e.g. German or Italian, but mostly just means "pricing scheme" there, like in the article ("import duty" using a different expression in those languages).
Might be a mostly/somewhat "false friend" for a German (pv magazine is german).
Tarif/Tarife means price list of anything. Your barber, restaurant, taxi service, hospital can have one. tariff as in the meaning of custom tax is a very narrow meaning considering the usage of the word in general (but that's OK).
Import duty is "gümrük vergisi", and the general list of this is "gümrük vergisi tarifesi" in broad sense. It also has a more technical name here but both I don't remember it, and it doesn't matter in this context.
In the Japan's context we would call it "elektrik fiyat tarifesi", or "elektrik tarifesi" for short, for example.
Likewise, many years ago, I got confused by less common meanings of the word "schedule". The most common meaning is a written or explicit arrangement of how a person or machine spends their time, particular for future planning.
The less common uses show up in examples like "Schedule I drugs" (highly banned) or various schedules in tax laws, appendices of long documents, etc.
Schedule is a note, it goes back to the Latin word for the strips of plant used to make papyrus sheets; so it's one of the strips and by analogy a written note small enough to fit on such a sheet.
Schedules are common in UK legislation as addenda to the main clauses/provisions. Most wouldn't fit in a papyrus strip though!
It’s confusingly super common in the US for that usage when talking about trucking and shipping. Where of course the other kind of tariffs are also common.
Some background info for context. (for those that may not be familiar).
Heat pump conjures up an image of an appliance, but it is a principle of physics. Heat can be created by burning fuel or electric resistance. Cold can't be created. Cold is the lack of heat. Cold is 'created' by removing heat. Fridge keeps the inside cool by moving heat from inside and dumps it outside. This movement of heat is called heat pump (pumping heat in a specific direction).
If we can do this for cold, we can also do this for heat. After all, we always have heat in the environment until we get to 0 degree Kelvin. Which means we can have heat pump water heater in the garage. Or heat pump furnace.
Creating heat from fuel/resistance is at most 100% efficient (most likely a LOT less). Heat pumps are 400% - 500% efficient per unit of electricity, because the idea is just to move heat. In one direction, or another.
All of this is great, until we get to the refrigerant used to transfer the heat. These are very specific chemicals. Mostly synthetic chemicals. Historically, these were Chlorofluorocarbons (CFCs). CFCs caused ozone depletion and have high GWP of 14,400.
What is GWP? CO2 is a warming gas that has Global Warming Potential (GWP) of 1 (the standard). Earth radiates heat back into the atmosphere (exactly the same as get from Sun) and CO2 acts as a barrier for the radiated heat from earth, retaining heat in the atmosphere and warming the planet. Why Greenhouse Gases Make the Planet Warmer: https://www.youtube.com/watch?v=AIBk0pGV_BQ
But, there are lots of other gases that have higher GWP. Fluorinated gases: Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic gases used for refrigeration (maybe other applications). Fluorinated gases replaced CFCs, which were causing ozone depletion. But they have high GWP. HFCs: up to 12,400, PFCs: up to 11,100, NF3: 16,100, SF6: 23,500 (https://www.epa.gov/ghgemissions/fluorinated-gas-emissions)
So, we have to find better alternatives for refrigerants. Because, these leak. And everybody on the planet is going to buy ACs. CO2 is a terrific refrigerant because it has GWP 1 and leaking of CO2 is perfectly okay. With 40 - 60 billion tons of CO2 from fossil fuels, CO2 leaks from refrigerants are less than a rounding error.
All good points. So, why don't we use CO2 in minisplits? Split systems are most popular in new construction and retrofits, so why are we settling for modern refrigerants like R32 with a large GWP of 675?
It's because CO2 has to be run at more extreme temperatures and pressures, fine for factory-made connections inside a single unit but a showstopper for field joints.
And also we have a large overabundance of CO2 we need to figure out something to do with, and using it in the heat pumps we’re all going to need to adjust to our overabundance of CO2 seems like a quite parsimonious arrangement.
Thanks for this summary. Very useful and informative.
After the 2026 heat wave in Europe and elsewhere, and expectations of things getting hotter with global warming and El Niño, it’s already past the time to prepare, but better late than never.
Will governments have to subsidize solar/inverter/battery/heat pump systems to keep people going?
What are people doing to get ready for a “hot house Earth” future around the world?
The only reason CFCs exist is because the US established a de-facto ban on propane as a refrigerant. You can't trademark, copyright it, or any other form of IP.
How is that a de facto ban, you can't trademark the common names of plenty of substances ubiquitous in daily life. The manufacturers of refrigerants don't seem like they could completely dictate what appliance manufacturers choose to use in their products.
It seems for refrigerators there are actually specific carve outs in EPA venting regulations to allow R-290 (propane) along with a couple others.
If vendors don't use it, possibly due to flammability, whether a real risk or as imagined by consumers that's a completely different situation. I can't find anything claiming it's banned or even discouraged by the government.
There are commonly sold flammable refrigerant things now in the USA, I see a bunch of small fridges using alkanes and cycloalkanes, not sure about HVAC.
CFC is a fluorinated gas. Its in the name. Chloroflurocarbon. So you're saying "Fluorinated gases replaced [fluorinated gasses]".
CO2 is not a terrific refrigerant. It requires comparably very high pressures to be effective and has a low critical point reducing their effectiveness in a lot of normal temperature ranges. More modern refrigerants like HFOs usually have a GWP of <1 and don't require anywhere near as high of pressures, with R-454B being around the same as R-410A.
R-454B contains HFO-1234yf, which has a trifluoromethyl group. Upon release to the atmosphere this ultimately forms trifluoroacetic acid, which has an extremely long residence time in the oceans (perhaps as much as millions of years, if I understand correctly).
Looking back at the comment I probably come across as overly hash, sorry.
FWIW, one of the biggest negatives to HFOs is that while they rapidly break down in the atmosphere they end up producing trifluoroacetic acid. This stuff then rains back down, and is a polyfluoroalkyl substance (PFAS).
Europe is using lots of refrigerants like r600 (isobutane) and r290 (propane).
They work really well, with the downside they are very explosive. However stories of airconditioners blowing up are really rare - it seems the risk is probably worth it for the environment.
I've been recharging the AC system on my vintage daily driver — a late 1960s Mercedes-Benz sedan — with common off the shelf campstove propane for 30 years. Keeps me cool regardless of outside Los Angeles heat. Requires a bit of care while doing a recharge, but it's nothing too crazy. My grandfather ran a dairy farm in Connecticut, he showed me this trick in the 80s. We used propane to keep all the cooling equipment in the milk houses running smooth back then. I'm curious about isobutane now.
Propane, butane, etc. are not explosives. They are not going to just energetically decompose. They are combustible, but it turns out most things worth having on earth are combustible
Indeed - it is only explosive when it leaks out and mixes with air in the correct quantities. Unfortunately this happens occasionally - with the common case being someone trying to use a knife to get ice out of a freezer or AC which is frozen up and accidentally cutting into a pipe.
They're pretty explosive when they have the right mix with air. This can easily happen in, say, a utility closet with a water heater or air handler, or a fridge in a kitchen, etc.
A small leak on the outside unit probably isn't going to be a big risk. A small leak on a unit in a closet with stuff that sometimes makes small sparks...
Japan is so far ahead the rest of the world for quality and innovative heat pumps. Quiet, robust, high efficiency in cold climates. I wish they could bring the prices down though.
I worry in 15 years we will all have crapily made Chinese heat pumps for a fraction of the cost. Noisy, not robust, copying competitor designs not innovating, lower efficiency but easily replaceable. Theres probably an analogy here with software talent and AI but its too early to do that.
I'm a big fan of Chinese lenses. I reach for Japanese and German lenses when I want to take the highest quality photographs that look like the photographs all the other photographers take. When I want to take a picture like you've never seen before I reach for
It's true a $3000 lens from Sony has better optical quality than a $300 lens from China, like take a picture of a starry sky and you will see light rays bounce around a lot more inside the Chinese lens. But in terms of value and innovation Chinese lenses have a place, and many Chinese manufacturers are looking for this kind of opportunity for whatever they make.
China figured out how to make thermal imaging sensors as well. Why would you buy a $4,000 Flir with less resolution when you can get a $400 Topdon. What's funny is now it appears Flir has cut their prices dramatically to compete.
I have Haier Arctic heat pumps that are made in China. They've been great so far. I've also worked with suppliers in Shenzhen for one-off custom electronic devices that would put western companies to shame in their communication, efficiency, turnaround time, cost, and engineering quality. The new transmission I just put in my truck was made in China too.
I never said that Chinese goods are crap. They seem to reside in the higher middle for HVAC. My argument is that if your business is a copy cat and the produce at scale - we cull the talent and model to build truly innovative products - since there isn't funding the innovation.
PRC's been white labelling / JV components for tier1 HVAC brands for 15 years now, they're fine quality/lifespan wise. Flagship PRC heatpump already caught up to JP in HSPF2 @ ~11 (GREE). Either way, more cheap commoditized heat pump = more installations = more aggregate global efficiency - every $ spend on JP premium is inefficient allocation of resources in terms of maximizing global energy savings.
Arguably, PRC price / value engineer is their innovation and by far more MORE important than vs minute efficiency differences. Ultimately it's about TCO and global adoption, if JP can't bring their prices down, if they can't fractionalize cost, then they're doing more harm than good for net transition - there's better things to with that 30-50% premium.
Oh I totally get their game - and its a smart one. Flood the market, own the distribution and servicing and you win the game. I feel like the GREE product is tier 2 but most people don't care. Its not comparable to the well made products - they aren't junk but they aren't quality either. PRC seems to have targeted the broad market - smart move.
Id argue that the PRC price / value engineer is only viable because of the development that the innovations in heat pumps have managed to provide. Can't have one without the other. Though once price / value owns the market - innovation dies.
Midea/GMCC, Gree spend ~5% of revenue on R&D like rest of industry, except they're larger vs JP companies (multiple size of related JP conglomerates & magnitudes larger than JP niche thermal management companies). Also more directly focused on thermal management/hvac (i.e. Gree doesn't have defense/space like Mitsubishi to split R&D). Then factor in PRC PPP, PRC simply spending magnitudes more on R&D and will continue to (involute vs domestic competition). Hence most of the tier1 western suppliers are now using white labelled / rebadged components (compressors etc) that are designed by PRC manufactures.
PRC just doing innovating AND value engineering - they have both. IMO with respect to energy efficiency tech is one of those "any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands". The primary metric for "quality" of energy transition products is efficiency / $, and in that JP fails hard. Only PRC is scaling efficiency / $ effectively, which has much greater value than JP trying to push top end, because frankly that's all they can do. Which has it's economic rational, i.e. TOC in wealthy countries where installation/labour expensive, but its still net, lower "quality" innovation because $ spend on JP premium nets less aggregate efficiency.
I live in the EU and have a heat pump clothes dryer. It takes a little longer than hot air, but it doesn't heat up as much and destroy clothes. It also doesn't take special voltage/plug. Any regular plug will work. All it needs is a drain - no waste heat vent required. Oh, and it's super quiet.
Chinese brands have all but caught up, they're within a few percentage points in performance, but 3-4x cheaper.
The additional cost barrier being you can't self install or Mitsubishi or get any warranty on a self install, which means you'll likely pay 5-10x when you include install.
Inferior quality maybe was accurate 5 years ago. Now they're taking over the global automotive market. Only thing preventing them from pulling another Japan-in-the-90s against the US auto market is americans' love of oversized trucks, tariffs, and import controls. If we had a true market economy, we'd see more BYD's than Teslas (and in most global markets that's already the case).
Yes, you can still get cheap Chineesium crap off Amazon for pennies on the competitor's dollar, but it's no longer necessarily true that Chinese = inferior.
This China craze won't last long. The Chinese PV export market crashed couple months ago(down 30% YoY), and it seems like their domestic auto market crashed too(down ~25% YoY since August).
It's just not as prevalent in the residential HVAC market (which this product serves?), and more in the commercial/industrial space (probably because of the higher pressures needed to get into a liquid state).
It's useful though, as I think (correct me if I'm wrong) that the gases generally used in HVAC tends to have much worse warming effect than co2 per volume.
We do need heat pumps deployed at large scale, but sometimes I worry we don't understand they need to be handled with care at the end of their life
Yes, that dangerous effect is indexed as GWP - global warming potential.
CO2 has a GWP of 1 in this context, while other refrigerants are worse - for example, R32 has a GWP of 675 (so 675x worse if it escapes), not sure about R290 (Propane), which I believe is either about 40 or 14…
Regarding EoL: At least around here, household appliances such as fridges are brought to a recycling yard and are properly taken care of in that regard… and as for heatpumps - those are only to be installed by certified professionals, for this very reason.
The global warming potential of hydrocarbons as such is generally overblown, since they oxidize into CO₂ in the atmosphere with a half-life of a decade or two.
That's true, old school refrigerants like R-12 are awful. The downside of modern replacement refrigerants are high operating pressure (>100 bar for R-744/CO2) or high flammability for natural refrigerants like R-290 (Propane) and R-600a (Isobutane).
But these are solely engineering problems, and I'm happy to know that my R-290 heat pumps at home (Panasonic L & Wolf FHS) and A/C (Midea Xtreme Save Blue) aren't awful to the environment, once they reach EOL.
The neat thing about propane as a refrigerant is that it's a really powerful one, actually rather better than R12 in practical applications.
If you replaced an R134a fill with R290 you'd need about half as much gas and if it got out, it's got a Global Warming Potential of 3, making it three times as bad as carbon dioxide and about 475 times better than the same amount of R134a.
Even in a very large air conditioning system like in my elderly Range Rover, the 500g or so of propane it would need is about the same as the engine sucks up in about four miles.
The effect of that escaping into the atmosphere is about as bad as the amount of petrol you spilled the last time you refilled your lawnmower.
If you're worried about the ZOMG IT IS GAS IT WILL MAKE A GINORMOUS EXPLODISHION aspect like a lot of people are, ask yourself this - how many aerosol cans are in your car right now? Tin of deicer, tin of magic tyre inflater, maybe a tin of air freshener or WD40 or something? You're already carrying more propane around with you, rattling around loose at your feet.
Mostly yes, you need to vacuum it down well and make sure you have compatible oil in the compressor. Some types of plastic tubing aren't particularly compatible but for cars it's okay.
Yeah, ammonia can also be used, it's, IIRC, more efficient to use it and a bit safer because you don't high pressure, buuut enough ammonia in the air will suffocate you.
It's lighter than air so it will go away by itself if allowed to. For a purely exterior instalation it's much better than anything else.
I have a heat pump that uses R290 (propane) (as well as an CO2 one for hot water) and would take that any day of the week over ammonia! The charge of propane is pretty tiny and the safety standards extremely strict, so not really concerning in terms of flammability, ammonia I would consider far, far more dangerous.
Would mandating the use of CO2 as a refrigerant also somehow economically motivate efforts to capture more CO2 out of the atmosphere, in a kind of virtuous cycle? Or would there be a Cobra Effect in there somewhere? I'm not familiar with the industries that refine and bottle the stuff.
No, neither - the amount of CO2 that'd be needed for use as a refrigerant is insignificant. There's already a lot of CO2 produced as a byproduct of industrial chemical processes like petroleum refining. Some of it is captured for reuse (e.g. in drink carbonation); most of it is released to the atmosphere.
Because they're sensible heat machines, instead of latent heat machines. In a perfect frictionless vacuum, both of these can achieve the same theoretical efficiency. In practice, not so much. In particular, the isothermal heat exchange of the ideal Stirling cycle requires heat exchangers with no thermal resistance (and therefore no temperature difference). A latent heat pump has a much easier time to very closely approximate isothermal heat exchange because condensation/evaporation temperatures at a given pressure are essentially constant.
If it is outside you can just use propane as refrigerant. Low warming value and it leaking to outside doesn't matter, not gonna catch on fire.
There are indoor devices using propane but they generally come with caveat "must be installed on room at least this m3", precisely so if it leaks it doesn't get to density that allows explosion
I believe there are propane using split AC systems where propane is used only in the outside unit. The outside unit has a heat exchanger transferring the heat to some glycol-water solution which is what then circulates through the inside unit.
I currently have R410a heat pumps with minisplits, when they're off warranty sometime in the future I might consider putting propane in them. The main question would be whether the oil used with R410a is compatible with propane as a refrigerant.
This is probably a little bit "dangerous" in the sense that I'll have high pressure propane in the line sets and minisplits inside the house, but it's a very small volume of propane and not really any more dangerous from a fire perspective than my propane fired condensing gas boiler.
[edit] a little internet sleuthing indicates that hydrocarbon refrigerants "might be" compatible with basically any oil, so I can probably just continue using whatever oil is in it.
This has the useful property of being regulation-exempt because it's already literally everywhere. Unlike "F gases", which have much more serious greenhouse effects and are regulated in the UK (and elsewhere): https://www.gov.uk/government/collections/fluorinated-gas-f-...
You could install your own CO2-based heat pump in a way you wouldn't be allowed to do with a F-gas based one.
OTOH, CO2 uses much higher pressures and so I'm more willing to DIY a F-gas based one. CO2 if there is a leak can cut a limb off. F-gas is generally not that high. I wouldn't want a leak/mistake, but CO2 is less personally forgiving.
There are resident systems, and they're of exactly the type listed in the article (i.e. water heaters). Residential... area heating pumps, so to say, are moving towards propane (afaik). I've been looking into getting a propane monoblock air-to-water pump, with an antifreeze loop towards an indoors heat exchanger / water tank.
Trends for new refrigerant depends on country... some to R-454B, and some to Propane, doesn't seem like C02 is very common which is a pity because I love the idea of a non-toxic non-flammable super cheap refrigerant.
This is for the Japanese market so perhaps the cons of the C02 systems are outweighed by the safety aspects.
CO2 does better with large temp deltas, like hot water tanks. Radiators don't produce large deltas - the inlet to outlet diff is typically under 10 degrees. But they run at higher pressures, making the manufacturing more expensive.
I heard CO2 is a gas with a powerful green house effect. What happens at the end of life of these units I wonder? What if they leak and it gets into the atmosphere!
So, in the US, for instance, the average person leads to the emission of 16 tonnes of co2 per year. The amount of co2 in your domestic heat pump (which… doesn’t weigh multiple tonnes) is more or less immaterial, even if it does leak.
Maybe but at this point I no longer think it's fair to be quite this dry on something that quite so many people would be legitimately sincere about anyway so I wouldn't exactly apologize for being the victim.
There is no reason not to use propane or butane, they have low global warming potential and is cheap. The fire risk is overstated, no one thinks twice about carrying a lighter in their pocket.
Solar water heaters (including evacuated vacuum tube) are great for efficiency, but PV has gotten so cheap and reliable that it's almost never worth a dedicated solar water heater unless you're extremely constrained for space.
Any electric or heat pump water heater that can have its thermostat digitally controlled could be combined with a thermostatic mixing valve hooked to the cold water line and used as a heat battery. When electricity is cheap/solar is producing have set the thermostat to the highest value it allows. Otherwise set it down to the the lowest comfortable value(~120F). The thermostatic mixing valve will mix the hot water with cold water to meet the comfortable value regardless of where it's at in the tank and the insulation will keep the water hot for hours after it's heated to the maximum.
The Japanese "EcoCute" heat pump water heaters like this one all work like that. Our very similar in specs Mitsubishi unit keeps the internal temperature at 80 C, and the electronic control panel in the bathroom/kitchen let you choose separate temperatures for bath water and hot tap water which it blends to match
I am working on a 5-10 year design a house and desperately hope monoblock air to water heat pumps with r744 (co2) are mature in the US market then. There are some, but it is still niche.
I am not a big fan of running lineset with r-410a or r32 in a confined space, too much risk of someone accidentally puncturing it. I would love hydronic systems to be more popular in the US. Being able to run hot/cold water in pex is stupid easy in both new construction and cheap in labor/materials. no noise concerns like forced air and much better routing for MEP imo. combined with an ERV, you can build a very good, high effiency zoned system that is comfortable and flexible.
I live in Ohio in a 100 year old home with cast iron radiators and a natural gas boiler and a gas water heater. I’d love to move to electric but it feels like my only real option for keeping the cast iron is something like the Daikin Altherma 3 H HT. Does anyone more knowledgeable of this part of the industry know of any reasonable alternatives for electrifying old houses but keeping the radiators?
Don’t forget to include the natural gas utility distribution costs when calculating any potential financial benefit when looking to switch to fully electric. Your not only getting rid of the natural gas Energy costs, but since your in Ohio, I’d wager your actual Distribution costs for your natural gas supply is actually greater than your actual Natural gas energy Supply costs.
Reducing to simply one utility distribution cost will help substantially when looking at long term financial viability
Gas is an important redundancy that will be a huge loss to give up. Not merely the 2nd source of energy, but in a totally different form with totally different pros, cons, and failure modes.
It's exceedingly useful that you can run all your gas appliances at full power at the same time without needing the ridiculous amount of copper or aluminum it takes to carry the same load in electric form, and do all that while the power is out, because the power is up on poles and the gas pipe is in the ground.
Now imagine trying to replace the redundancy by ups or generator. The amount of copper, electronics, and batteries needed to make a ups that can run your furnace or ac and your stove and hot water is just ridiculous. Most people simply won't have it. Wildly impractical luxury.
It's kind of ridiculous to require $billion chip fab infrastructure to make heat, and have your stove be this delicate piece of complex electronics and the burners are all these fixed little circles that don't heat pans evenly because it costs more money to make the fancy burners large enough to cover a whole pan.
Meanwhile a gas stove is just a couple chunks of dead metal and almost no moving parts and doesn't even need electricity let alone any electronics. That is a huge practicality and robustness win.
And heats pans more evenly because the flame does not have this weird artficially sharp 0%/100% border. Even a small simmer burner heats a large pan more evenly because although there is a hotter spot in the center, the flame still spreads out and travels along the pan and up the sides no matter what size it is. It doesn't care what size the pot or pan is, and also doesn't care what the pan is made out of. That is huge.
Electronics and heat are not natural together. It's a constant fight to try to prevent heat from killing elctronics. Every day that one of the thousands of electronic parts of an inductive range sittng above a hot oven and below a hot pan doesn't fail is a lucky day. It's not just reliable by default by just being simple.
What you say is all well and good, but the reality is that most gas appliances do not work without electricity. Your stove is about the only thing that can work on gas alone. The furnace, the water heater, the dryer, they all need electricity.
So you need backup electricity either way. And in the case of a furnace it's still a significant draw due to fans and/or pumps so to get multi-day resilience you need a big battery. Less than if it was a heatpump, sure, but this battery and inverter system will use all the same amount of electronics either way.
But you pay $100 a month just for the ability to use the gas that you will then pay for. If you want fossil redundancy then go with a propane generator, sits on property as energy storage, available for use when needed. You’re also in at a relatively decent price, for a backup system.
That coupled with batteries and you eliminate that Distribution cost double up by having to be served by two utilities. Payback is under 2-5 years for that backup, when you account for the distribution cost elimination
A propane generator will not buy you much time or output.
If the home owner has natural gas? They should could get a natural gas generator, that way they have a continuous supply of fuel if the grid fails.
Grid and gas failure? That happens only after a significant event, like a major earthquake. Not much you can do about those sorts of events. ( The person lives in Ohio… so not as much concern. )
Cost-wise? They would be better with a dual fuel system for heating. They live in Ohio, they probably have AC so moving to dual fuel when the AC system needs to be replaced is the smarter option.
A friend of mine just got a generac generator, fully installed it was 17k. Pretty steep, not to mention the gas bill with any significant outage will be huge.
I appreciate the argument, but I can’t make my own natural gas. I was considering all electric with a backup wood burner insert in my chimney. I’ll probably end up with vehicle2home as a backup and solar panels, maybe not in that order. Natural gas is extremely good at generating heat, and I completely understand why people prefer it.
No one likes steam these days because it's old and difficult to install correctly or modify later, but steam has some really cool features.
First, it doesn't require a pump to circulate. That means both the mechanical reliability of not having the electric motor and rotating water seal, or any moving part at all(1), but also you don't need any electricity.
It doesn't even need the usual low voltage circuit for the thermostat and gas valve. These are not common but also not new, there are millivolt systems where the thermostat & gas valve run only on the electricity generated by the thermocouple on the pilot.
It means that when ice has taken down all the power lines in a region, and blocked all the roads for repair crews to fix them at the same time, your heat stays fully working. No air blower, no water pump, not even 24v for the thermostat, and not by dint of having a ups which is just more stuff to fail.
Same goes for the hot water and the stove but that's more about gas than steam.
There is no getting around the huge efficiency of heat pumps of course. It just still kills me that we are accepting it as normal to require TSMC and ASML $billion chip fab infrastructure to make heat. But I guess you could say the same about leds and light so whatever I'm not saying we shouldn't use heat pumps.
(1) there is a moving part in the vent that opens and closes on each radiator, but that is a quality of life and longevity thing. If the vent fails to close or seal, the radiator still works, you still have heat, it just makes a hissing noise and consumes more fresh water which corrodes the boiler faster so it may leak in 5-10 years instead of 20-never.
Honestly I wish there was a good way to burn wood in an insert to heat the water that goes through my radiators, to offset an electric system. We tend to get a lot of weeks in the 20 or 30’s where a decent air to water system might do fine, but it would be amazing to burn wood for a few days when it sits at 0.
I take your point, but what you’re describing would have to cost thousands just in putting in underfloor pipes. It will never make financial sense to do it? Or am I misinterpreting your suggestion?
I'm actually in need of a new hot water tank and have been looking for a heat pump one. Wonder if these will be available in Australia, and how they compare to the current range.
The Australian electronics YouTuber Dave Jones (EEVBlog) had a heat pump water heater installed in his house, and while on the outside it was branded "Reclaim Energy", it had a Made in Japan sticker and was internally a Mitsubishi.
But having water leave the building envelope is a bit scary on very cold days. There are heat traces and freeze valves so it should be fine, but I do worry about power outages during cold snaps
“Hitachi has not yet disclosed full efficiency specifications for the two new models. Their predecessors, the BHP-FV37WD and BHP-FV46WD, have annual hot-water and heat-retention efficiency ratings under Japanese Industrial Standards (JIS) of 4.2 and 4.1, respectively.”
I couldn't find a model/calculator that would help visualise typical COP values for particular climatic conditions. However, you'll find in your travels that a COP of ~2-2.5 is typically achieved for ambient (outdoor) temperatures of -15oC (for air sourced heat pumps).
If 300L of water at 15oC is filled into a tank and needs to be heated to 60oC within 2 hours during ambient temperature of -15oC, you get very approximately (no thermal losses considered):
- An output energy need of approximately (4190300(60-15))/(60*120)=~8kW (56MJ/2h)
- An input electricity need of approximately (8/2.2)=~3.6kW
Instead of a resistive heating hot water unit requiring 16kWh to do this job, you could use a heat pump hot water unit requiring 7.2kWh, cutting electricity use in half.
And this is for arguably the most extreme use case for a heat pump hot water unit where it's "cold started" right at the coldest moment in Winter in cool-temperate climates (such as SE Australia). Think for example, arriving at a ski chalet and having to turn on the hot water unit before someone can take the first hot shower.
On a more typical day of the year, perhaps with overnight ambient temperature of 10-15oC, the COP would rise to ~4, equating to an electricity consumption of 2kWh to heat the 300L of water. A lot of units will be set to heat during the warmest part of the day, let's assume an ambient temperature of 25-30oC, where a COP of ~5-6 is more typically achieved. However, there are obviously diminishing returns for COP of 4 vs 5.
In arctic climates, heat pumps are still used, but with a ground or aquifer source rather than ambient air source.[2]
These tend to work fine down to -25° C or so ambient temperature (you lose some efficiency below -5° C or so), so should always be outside. Obviously you need an alternate source of water heating if you live somewhere where it routinely gets below that, but even in a lot of places like that you could set it up to use the heat pump 90-95% of the year and a cheap but far less efficient resistive heater for the very cold days, and still come out far ahead.
Technically your refrigerator heats up your kitchen in the same fashion adding extra work for your AC to compensate.
Unless you live in the artic where it's freezing year round, these things make sense. During the summer they reduce your cooling load and during the winter they are effectively heated by whatever your home heater is. Meaning if it's gas, then they are gas powered. If you have a heat pump outside then it's still pretty efficient. Even in the worst case of a resistive heater you are basically just running a slow resistive heater.
Most homes in Japan for decades have been designed for Tankless Gas Water Heaters stuck on the side of the building so there is no room indoors for a water tank.
The condenser unit for this literally just looks like the same one as for a regular mini split air conditioner, just a little bit larger.
One of the main reasons I went heat pump electric in my house (I could have paid less and stayed with tankless LP gas hot water) is I'm just not that comfortable with gas, especially living in an earthquake-prone country. Even if there aren't leaks it's terrible for indoors air quality, and a worry when you have young kids.
I was worried going from living with tankless to a tank that we would run out of water like we did in my parents house as a kid but so far it's just never been a problem. I think it helps that while the physical water capacity of our unit is 370 liters, the internal temperature is 80 C and it uses a thermostatic valve to blend the output, so the "hot water capacity" is more like 500 liters.
which is why the bit thats sourcing the heat/cold is outside your house. it either has a massive radioator and fan, or pipes undergorund to source/sink the heat
Technology Connections has recently published an in-depth piece of the advantages and disadvantages of in-room heat-pump water heaters [1].
The tl;dw is that it is significantly slower than a resistive or gas-powered water heater, and lowers the temperature of the room by a few degrees, but nothing major. You have to over-provision them compared to your needs. And they are way bigger.
> significantly slower than a resistive or gas-powered water heater
This was TC being a weirdo. He bought a 120V hot water heater. Had he done a regular 240V water heater the recovery time would be comparable to pure resistive water heaters.
But the takeaway about cooling is important. These things barely chill the room they are in.
If 4.2 (or 4.1) is really the annual coefficient of performance (turn 1kWh electric energy into 4.2kWh heat energy) then this is a very good value.
Because heating water requires higher temperature differences (usually heat pumps get more inefficient then). And with an "ordinary" (propane) heat pump you get such high numbers only in summer time (>=20°C) and for water temperatures of max 50°C.
I believe that for every joule of electricity used, 4 or 4.1 joules are pumped from the environment into the water. This is contrast to conventional water heaters which are bounded by an efficiency of 1, where, for example, burning gas directly heats the water with some heat leaking into the environment instead of the water.
We have one of the "all-denka" electric plans, where we trade off cheap rates during solar hours for expensive rates during duck curve hours. By having the hot water only run during cheap hours, and having the aircon turned off/down during the expensive hours, we're paying less in energy for our all-electric house than we did in combined electric+gas in our 3x smaller apartment.
We pay approx (before fees, and the rates change slightly by season):
* 8 AM - 10 AM: 35 yen/kWh
* 10 AM - 4 PM: 13 yen/kWh
* 4 PM - 6 PM: 35 yen/kWh
* 6 PM - 8 AM: 19 yen/kWh
Our Mitsubishi has other nice features like it can recirculate the water in the bath through a heat exchanger after you already filled it and got in, so it will keep the water from cooling down to lukewarm, and you can even adjust the bath water temperature if you ended up with filling it with too warm or too cold water. Of course, there's also an app so you can start filling up the bathtub when you leave work for home so a hot bath is waiting for you. There's also an intercom to the kitchen "so mom can tell the kids to get out of the bath, dinner is ready".
edit: the wifi integration does have one actually useful feature: if we had solar panels, then it can use data from them to know when to run "for free", and it can use weather data to predict if it should wait for sun or not to run
Interesting! Is there some sort of filter system you can easily clean out, to avoid any issues?
How long do you sit in a bath?
> Of course, there's also an app so you can start filling up the bathtub when you leave work for home so a hot bath is waiting for you.
My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
Another Japan resident here! It is common for a family to share a bath for the evening. (One at a time!) This works because each person showers to get clean before you get in the bath. Many also have folding bath covers, which help to avoid the water from cooling down and to keep the water clean during the showers. Still, nobody wants to be last.
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
A smart reaction! But most baths are also whole-room units, with a floor drain, and are intended to get wet. I myself have forgotten to stop the bath water a number of times (neither I nor my bath are so "smart") and while it is an unfortunate waste of water, there is no danger of flooding, only slight embarrassment.
BTW, Japanese bathing is somewhat visible in My Neighbor Totoro, a really cute movie.
Nice concept! Do you have any problems with mold build up?
That's unexpected.
80kg of meat can hold a lot of heat. It cools quicker than you think it would. Also, Japanese families often share the bathwater within themselves(but everyone showers outside the tub first), and the water will become lukewarm at some point in that use case.
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
Yep, remotely operating a machinery will always have some risks. Every machinery should have someone with an emergency stop button should be monitoring it at all time, ideally. But it's a well engineered tub auto-fill in the shower room, it effectively belongs to "inherently safe" category of equipment.
This is uncommon in the US, so a bath overflow quickly becomes a significant structural issue.
It's the metal plate usually just below the faucet that looks like it might be useless. But it has an opening underneath to let the overflow water in. These are always sized to handle more water than the faucet can output.
This is basically a non-concern in anything but very, very old, unremodeled bathrooms.
The sinks do as well, but it is more obvious.
But the sibling comment to this one, where a sink had an overflow, but it was not connected, did not meet code [also 1].
Go figure. There must be some reasoning there, but I'm confused as to what it is.
https://forms.iapmo.org/email_marketing/codespotlight/2018/m...
I'm an American and my answer is at least an hour, maybe more, depending on how I'm feeling. I usually listen to an audiobook. Baths are for hanging out and relaxing in.
We love our baths here in Japan
> My immediate reaction to this is, “there’s a way for my house to be remotely flooded”.
I forgot to mention that it senses and automatically stops filling the bath at a select number of liters, even if you start a bath using the physical button when you're at home.
You can totally remodel bathrooms to be "wet rooms" in the US, it is well worth it.
Kids flooding the bathroom via the tub? Not a problem. Toilet overflowing? Gross, but not a problem.
I wish I would have made all the bathrooms in my home wet rooms.
Contrast this with the all-in-one design where a person taking a shower monopolizes all the plumbing fixtures even while they are not using them. I was on a bachelor party trip with 8 guys and two bathrooms where some inconsiderate people camped out in the shower for 20 minutes while people waking up had to pee so badly they went outside in the bushes. Meanwhile on a trip to Japan with five people we could easily share one or two split bathrooms and never had an issue.
Oh, and the electric bidet is a clear winner in terms of bathroom accessory to buy. Less TP use and no threat of swamp ass that demands you take a shower. Heated seat in winter is a blessing, especially in the morning. After my Japan trip it was the first thing I bought when I got back home.
The entire point of a bath is to relax and soak in it. Otherwise I'd just take a far more economical shower.
Depends on setup, of course. If there's a central AC blowing hot/cold air through ducts, you're stuck using a grey water loop. But it is the least attractive setup...
These are truly _bath_ rooms. The shower and bath are side by side, with the intent that you wash off before hopping into the bath to soak. Thus if the tub overflowed it would just go down the shower drain.
Having two options during cold winters can pay for itself with one emergency repair though, or be a massive savings if it can't be fixed fast enough and pipes burst.
That alone probably will make a huge difference in how often you have to deep clean it.
I mean you can as long as you make the bathroom a wet room and shower outside the tub, which is exactly how the Japanese do it.
I've also got the ecocute but I was told that it's cheaper to just pump fresh hot water into the bath than recirculate the cooled down water. It uses less energy to pump the already boiled water into the tub than to heat it back up.
Though fresh water and letting out the old will clean the water you are soaking in, which may be valuable.
My rates are 36yen from 6am to 10pm and 19yen on the other end.
Re-reading my earlier post, I should’ve said cost and not energy.
However this is somewhat old fashioned, the most modern tarrifs vary on a 30 minute window, with prices set a day ahead. If there's a lot of solar and little demand on say a sunny sunday afternoon or windy february nighttime, then the prices may even go negative.
You want your consumption to be tied into there. You can do this with batteries -- for example on Tuesday I used 34kWh, 24kWh overnight (mainly to charge the car) and 10kWh in the day. If I had a battery I could have charged that battery overnight and saved a couple of quid, or about £600 a year (depends on what my daytime usage is)
However with a 30kWh battery I could have charged it on Sunday afternoon and been paid for that, and not used any power on Monday, Tuesday or Wednesday for the house. But then the agile rate last night was 25p/kWh. I did look at getting a battery and inverter installed but it wasn't cheap.
On top of that you've got self generation. I have very little solar generation, but in theory I reckon I could have 8kWp on the roof -- I'd want to charge the car (and house battery, and any heatpump or ac) when the sun was shining then, which would be even cheaper than charging at night. Home Assistant will do that, but it feels a little fragile with my car charger (if the HA dies, the charger won't start, and then I can't go anywhere. It's not a great charger)
In fairness it probably works ok for homes insulated to a much higher standard than most British ones.
I'd love to have something like that!
Whenever I take a hot shower I fantasize about putting in a liquid-to-liquid heat exchanger so the hot water can heat up the cold water and you can run the hot water at a much lower temperature.
This application with the bath tub feels way more justified.
I was quite confused at the use of "tariff" here, as it meant to me a "tax on a good crossing a political boundary." Turns out, 'tariff' has an older meaning: a published schedule of fees or taxes issued by some authority.
For example in Turkish, "tarife" means only that: Conditional / Schedule-based pricing, and according to Sevan Nişanyan (a language researcher), Turkish borrowed it from Italian, where it was being used similarly. Import tariffs are a completely different word.
It apparently came to English through Italian -> Spanish -> French.
So I'm not a native English speaker but as far as I understand, import tariffs are just one kind of tariff.
ps. I just f'ing love Etymology.
https://www.etymonline.com/search?q=tariff
Spoiler: the word is originally from Arabic :)
"Tarief" just means price of mainly a service.
I think 'dynamic rate' is the proper translation for the US?
The same word exists in e.g. German or Italian, but mostly just means "pricing scheme" there, like in the article ("import duty" using a different expression in those languages).
Might be a mostly/somewhat "false friend" for a German (pv magazine is german).
Import duty is "gümrük vergisi", and the general list of this is "gümrük vergisi tarifesi" in broad sense. It also has a more technical name here but both I don't remember it, and it doesn't matter in this context.
In the Japan's context we would call it "elektrik fiyat tarifesi", or "elektrik tarifesi" for short, for example.
Cheers,
Your friendly Turkish HN user.
The less common uses show up in examples like "Schedule I drugs" (highly banned) or various schedules in tax laws, appendices of long documents, etc.
Schedules are common in UK legislation as addenda to the main clauses/provisions. Most wouldn't fit in a papyrus strip though!
When I see "tariff", my mind only thinks of 関税 , and I was just as confused as you were. Turns out its just an item in a price schedule.
Heat pump conjures up an image of an appliance, but it is a principle of physics. Heat can be created by burning fuel or electric resistance. Cold can't be created. Cold is the lack of heat. Cold is 'created' by removing heat. Fridge keeps the inside cool by moving heat from inside and dumps it outside. This movement of heat is called heat pump (pumping heat in a specific direction).
If we can do this for cold, we can also do this for heat. After all, we always have heat in the environment until we get to 0 degree Kelvin. Which means we can have heat pump water heater in the garage. Or heat pump furnace.
Creating heat from fuel/resistance is at most 100% efficient (most likely a LOT less). Heat pumps are 400% - 500% efficient per unit of electricity, because the idea is just to move heat. In one direction, or another.
All of this is great, until we get to the refrigerant used to transfer the heat. These are very specific chemicals. Mostly synthetic chemicals. Historically, these were Chlorofluorocarbons (CFCs). CFCs caused ozone depletion and have high GWP of 14,400.
What is GWP? CO2 is a warming gas that has Global Warming Potential (GWP) of 1 (the standard). Earth radiates heat back into the atmosphere (exactly the same as get from Sun) and CO2 acts as a barrier for the radiated heat from earth, retaining heat in the atmosphere and warming the planet. Why Greenhouse Gases Make the Planet Warmer: https://www.youtube.com/watch?v=AIBk0pGV_BQ
But, there are lots of other gases that have higher GWP. Fluorinated gases: Hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride, and nitrogen trifluoride are synthetic gases used for refrigeration (maybe other applications). Fluorinated gases replaced CFCs, which were causing ozone depletion. But they have high GWP. HFCs: up to 12,400, PFCs: up to 11,100, NF3: 16,100, SF6: 23,500 (https://www.epa.gov/ghgemissions/fluorinated-gas-emissions)
So, we have to find better alternatives for refrigerants. Because, these leak. And everybody on the planet is going to buy ACs. CO2 is a terrific refrigerant because it has GWP 1 and leaking of CO2 is perfectly okay. With 40 - 60 billion tons of CO2 from fossil fuels, CO2 leaks from refrigerants are less than a rounding error.
It's because CO2 has to be run at more extreme temperatures and pressures, fine for factory-made connections inside a single unit but a showstopper for field joints.
After the 2026 heat wave in Europe and elsewhere, and expectations of things getting hotter with global warming and El Niño, it’s already past the time to prepare, but better late than never.
Will governments have to subsidize solar/inverter/battery/heat pump systems to keep people going?
What are people doing to get ready for a “hot house Earth” future around the world?
It seems for refrigerators there are actually specific carve outs in EPA venting regulations to allow R-290 (propane) along with a couple others.
https://www.epa.gov/snap/substitutes-household-refrigerators...
If vendors don't use it, possibly due to flammability, whether a real risk or as imagined by consumers that's a completely different situation. I can't find anything claiming it's banned or even discouraged by the government.
CO2 is not a terrific refrigerant. It requires comparably very high pressures to be effective and has a low critical point reducing their effectiveness in a lot of normal temperature ranges. More modern refrigerants like HFOs usually have a GWP of <1 and don't require anywhere near as high of pressures, with R-454B being around the same as R-410A.
Thanks! Could've worded it better.
FWIW, one of the biggest negatives to HFOs is that while they rapidly break down in the atmosphere they end up producing trifluoroacetic acid. This stuff then rains back down, and is a polyfluoroalkyl substance (PFAS).
They work really well, with the downside they are very explosive. However stories of airconditioners blowing up are really rare - it seems the risk is probably worth it for the environment.
Nearly all refrigerators/freezers in Europe are isobutane, and have been for 20 years.
https://www.youtube.com/watch?v=uJJvG10tUAw
They're pretty explosive when they have the right mix with air. This can easily happen in, say, a utility closet with a water heater or air handler, or a fridge in a kitchen, etc.
A small leak on the outside unit probably isn't going to be a big risk. A small leak on a unit in a closet with stuff that sometimes makes small sparks...
I worry in 15 years we will all have crapily made Chinese heat pumps for a fraction of the cost. Noisy, not robust, copying competitor designs not innovating, lower efficiency but easily replaceable. Theres probably an analogy here with software talent and AI but its too early to do that.
I'm a big fan of Chinese lenses. I reach for Japanese and German lenses when I want to take the highest quality photographs that look like the photographs all the other photographers take. When I want to take a picture like you've never seen before I reach for
https://www.venuslens.net/product/laowa-9mm-f-5-6-ff-rl/?srs...
or
https://findingrange.com/2022/01/14/7artisans-photoelectric-...
It's true a $3000 lens from Sony has better optical quality than a $300 lens from China, like take a picture of a starry sky and you will see light rays bounce around a lot more inside the Chinese lens. But in terms of value and innovation Chinese lenses have a place, and many Chinese manufacturers are looking for this kind of opportunity for whatever they make.
What's the innovation?
Arguably, PRC price / value engineer is their innovation and by far more MORE important than vs minute efficiency differences. Ultimately it's about TCO and global adoption, if JP can't bring their prices down, if they can't fractionalize cost, then they're doing more harm than good for net transition - there's better things to with that 30-50% premium.
Id argue that the PRC price / value engineer is only viable because of the development that the innovations in heat pumps have managed to provide. Can't have one without the other. Though once price / value owns the market - innovation dies.
PRC just doing innovating AND value engineering - they have both. IMO with respect to energy efficiency tech is one of those "any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands". The primary metric for "quality" of energy transition products is efficiency / $, and in that JP fails hard. Only PRC is scaling efficiency / $ effectively, which has much greater value than JP trying to push top end, because frankly that's all they can do. Which has it's economic rational, i.e. TOC in wealthy countries where installation/labour expensive, but its still net, lower "quality" innovation because $ spend on JP premium nets less aggregate efficiency.
The additional cost barrier being you can't self install or Mitsubishi or get any warranty on a self install, which means you'll likely pay 5-10x when you include install.
Inferior quality maybe was accurate 5 years ago. Now they're taking over the global automotive market. Only thing preventing them from pulling another Japan-in-the-90s against the US auto market is americans' love of oversized trucks, tariffs, and import controls. If we had a true market economy, we'd see more BYD's than Teslas (and in most global markets that's already the case).
Yes, you can still get cheap Chineesium crap off Amazon for pennies on the competitor's dollar, but it's no longer necessarily true that Chinese = inferior.
As for cars, sales of ICE were down 40℅, BEV grew 1.7℅
What happened since then?
China is now at a stage of economic development where it can manufacture products across the entire quality spectrum.
Japan went through a somewhat similar transition: in the 1960s and 70s.
* https://en.wikipedia.org/wiki/R-744
It's just not as prevalent in the residential HVAC market (which this product serves?), and more in the commercial/industrial space (probably because of the higher pressures needed to get into a liquid state).
We do need heat pumps deployed at large scale, but sometimes I worry we don't understand they need to be handled with care at the end of their life
CO2 has a GWP of 1 in this context, while other refrigerants are worse - for example, R32 has a GWP of 675 (so 675x worse if it escapes), not sure about R290 (Propane), which I believe is either about 40 or 14…
Regarding EoL: At least around here, household appliances such as fridges are brought to a recycling yard and are properly taken care of in that regard… and as for heatpumps - those are only to be installed by certified professionals, for this very reason.
If you replaced an R134a fill with R290 you'd need about half as much gas and if it got out, it's got a Global Warming Potential of 3, making it three times as bad as carbon dioxide and about 475 times better than the same amount of R134a.
Even in a very large air conditioning system like in my elderly Range Rover, the 500g or so of propane it would need is about the same as the engine sucks up in about four miles.
The effect of that escaping into the atmosphere is about as bad as the amount of petrol you spilled the last time you refilled your lawnmower.
If you're worried about the ZOMG IT IS GAS IT WILL MAKE A GINORMOUS EXPLODISHION aspect like a lot of people are, ask yourself this - how many aerosol cans are in your car right now? Tin of deicer, tin of magic tyre inflater, maybe a tin of air freshener or WD40 or something? You're already carrying more propane around with you, rattling around loose at your feet.
It's lighter than air so it will go away by itself if allowed to. For a purely exterior instalation it's much better than anything else.
It will suffocate you on account of all that blood pulp in your lungs. And eyes, and nasal mucosa...
Having a high pressure ammonia leak indoors is a death sentence for anybody in the same room. Same building, if it's large enough...
Looks like 30-50% less efficiency.
There are indoor devices using propane but they generally come with caveat "must be installed on room at least this m3", precisely so if it leaks it doesn't get to density that allows explosion
This is probably a little bit "dangerous" in the sense that I'll have high pressure propane in the line sets and minisplits inside the house, but it's a very small volume of propane and not really any more dangerous from a fire perspective than my propane fired condensing gas boiler.
[edit] a little internet sleuthing indicates that hydrocarbon refrigerants "might be" compatible with basically any oil, so I can probably just continue using whatever oil is in it.
You could install your own CO2-based heat pump in a way you wouldn't be allowed to do with a F-gas based one.
This is for the Japanese market so perhaps the cons of the C02 systems are outweighed by the safety aspects.
Compared to other refrigerants it's a paradise:
* https://www.epa.gov/hfcs/technology-transitions-gwp-referenc...
* https://en.wikipedia.org/wiki/Global_warming_potential#Calcu...
Almost anything else you could use as a refrigerant is worse.
Even water vapour is a worse greenhouse gas.
Edit: wait, have I been whooshed? Apologies if so... ;-)
Yeah, but I'm from the UK so I should be able to detect dry humour. It's something that Americans don't really get.
You know, like affordable healthcare.
Napkin math based on Amazon/Home Depot prices
You can get a 80"x90"x95% = 2kW output solar heater for $2000
or eight 45"x70"x25% = 1.8kW solar panels for $2800
A regular water heater needs about 12kWh a day, which is about what both systems would produce.
However, a heat pump water heater is 4x as efficient, so you could get by with $700 of solar panels.
Except, a heat pump water heater costs $2000 instead of $500 for a regular electric heater.
There's also install, maintenance, and the fact that we're talking about grid prices, not home panels, but those won't fit on my napkin.
Happy they named it EcoCute, that's so much better than ElectroCute :)
I am not a big fan of running lineset with r-410a or r32 in a confined space, too much risk of someone accidentally puncturing it. I would love hydronic systems to be more popular in the US. Being able to run hot/cold water in pex is stupid easy in both new construction and cheap in labor/materials. no noise concerns like forced air and much better routing for MEP imo. combined with an ERV, you can build a very good, high effiency zoned system that is comfortable and flexible.
Will see!
Perhaps look into "air to water" heat pumps.
It's exceedingly useful that you can run all your gas appliances at full power at the same time without needing the ridiculous amount of copper or aluminum it takes to carry the same load in electric form, and do all that while the power is out, because the power is up on poles and the gas pipe is in the ground.
Now imagine trying to replace the redundancy by ups or generator. The amount of copper, electronics, and batteries needed to make a ups that can run your furnace or ac and your stove and hot water is just ridiculous. Most people simply won't have it. Wildly impractical luxury.
It's kind of ridiculous to require $billion chip fab infrastructure to make heat, and have your stove be this delicate piece of complex electronics and the burners are all these fixed little circles that don't heat pans evenly because it costs more money to make the fancy burners large enough to cover a whole pan.
Meanwhile a gas stove is just a couple chunks of dead metal and almost no moving parts and doesn't even need electricity let alone any electronics. That is a huge practicality and robustness win.
And heats pans more evenly because the flame does not have this weird artficially sharp 0%/100% border. Even a small simmer burner heats a large pan more evenly because although there is a hotter spot in the center, the flame still spreads out and travels along the pan and up the sides no matter what size it is. It doesn't care what size the pot or pan is, and also doesn't care what the pan is made out of. That is huge.
Electronics and heat are not natural together. It's a constant fight to try to prevent heat from killing elctronics. Every day that one of the thousands of electronic parts of an inductive range sittng above a hot oven and below a hot pan doesn't fail is a lucky day. It's not just reliable by default by just being simple.
It's not a slam dunk all-upsides trade-off.
So you need backup electricity either way. And in the case of a furnace it's still a significant draw due to fans and/or pumps so to get multi-day resilience you need a big battery. Less than if it was a heatpump, sure, but this battery and inverter system will use all the same amount of electronics either way.
If the home owner has natural gas? They should could get a natural gas generator, that way they have a continuous supply of fuel if the grid fails.
Grid and gas failure? That happens only after a significant event, like a major earthquake. Not much you can do about those sorts of events. ( The person lives in Ohio… so not as much concern. )
Cost-wise? They would be better with a dual fuel system for heating. They live in Ohio, they probably have AC so moving to dual fuel when the AC system needs to be replaced is the smarter option.
No one likes steam these days because it's old and difficult to install correctly or modify later, but steam has some really cool features.
First, it doesn't require a pump to circulate. That means both the mechanical reliability of not having the electric motor and rotating water seal, or any moving part at all(1), but also you don't need any electricity.
It doesn't even need the usual low voltage circuit for the thermostat and gas valve. These are not common but also not new, there are millivolt systems where the thermostat & gas valve run only on the electricity generated by the thermocouple on the pilot.
It means that when ice has taken down all the power lines in a region, and blocked all the roads for repair crews to fix them at the same time, your heat stays fully working. No air blower, no water pump, not even 24v for the thermostat, and not by dint of having a ups which is just more stuff to fail.
Same goes for the hot water and the stove but that's more about gas than steam.
There is no getting around the huge efficiency of heat pumps of course. It just still kills me that we are accepting it as normal to require TSMC and ASML $billion chip fab infrastructure to make heat. But I guess you could say the same about leds and light so whatever I'm not saying we shouldn't use heat pumps.
(1) there is a moving part in the vent that opens and closes on each radiator, but that is a quality of life and longevity thing. If the vent fails to close or seal, the radiator still works, you still have heat, it just makes a hissing noise and consumes more fresh water which corrodes the boiler faster so it may leak in 5-10 years instead of 20-never.
Then run a wee bit hot water through your cast iron rads for the look of the thing.
CO2 refrigerant as well.
But having water leave the building envelope is a bit scary on very cold days. There are heat traces and freeze valves so it should be fine, but I do worry about power outages during cold snaps
https://en.wikipedia.org/wiki/Tariff_(regulation)
What does this mean?
I couldn't find a model/calculator that would help visualise typical COP values for particular climatic conditions. However, you'll find in your travels that a COP of ~2-2.5 is typically achieved for ambient (outdoor) temperatures of -15oC (for air sourced heat pumps).
If 300L of water at 15oC is filled into a tank and needs to be heated to 60oC within 2 hours during ambient temperature of -15oC, you get very approximately (no thermal losses considered):
- An output energy need of approximately (4190300(60-15))/(60*120)=~8kW (56MJ/2h)
- An input electricity need of approximately (8/2.2)=~3.6kW
Instead of a resistive heating hot water unit requiring 16kWh to do this job, you could use a heat pump hot water unit requiring 7.2kWh, cutting electricity use in half.
And this is for arguably the most extreme use case for a heat pump hot water unit where it's "cold started" right at the coldest moment in Winter in cool-temperate climates (such as SE Australia). Think for example, arriving at a ski chalet and having to turn on the hot water unit before someone can take the first hot shower.
On a more typical day of the year, perhaps with overnight ambient temperature of 10-15oC, the COP would rise to ~4, equating to an electricity consumption of 2kWh to heat the 300L of water. A lot of units will be set to heat during the warmest part of the day, let's assume an ambient temperature of 25-30oC, where a COP of ~5-6 is more typically achieved. However, there are obviously diminishing returns for COP of 4 vs 5.
In arctic climates, heat pumps are still used, but with a ground or aquifer source rather than ambient air source.[2]
[1] https://en.wikipedia.org/wiki/Coefficient_of_performance
[2] https://en.wikipedia.org/wiki/Ground_source_heat_pump
Which means in winter that is extra work for your heating system to compensate for
But in climates where heating only really runs in winter it's great
Unless you live in the artic where it's freezing year round, these things make sense. During the summer they reduce your cooling load and during the winter they are effectively heated by whatever your home heater is. Meaning if it's gas, then they are gas powered. If you have a heat pump outside then it's still pretty efficient. Even in the worst case of a resistive heater you are basically just running a slow resistive heater.
And for the normal ones, at least they are leveraging outside temperature parts of the time while everything else stays at 1 in 1 out.
Most homes in Japan for decades have been designed for Tankless Gas Water Heaters stuck on the side of the building so there is no room indoors for a water tank.
The condenser unit for this literally just looks like the same one as for a regular mini split air conditioner, just a little bit larger.
I have a tankless in my house and I'm not going back... I wish someone made a heat pump tankless water heater (I don't know if that is possible)
I was worried going from living with tankless to a tank that we would run out of water like we did in my parents house as a kid but so far it's just never been a problem. I think it helps that while the physical water capacity of our unit is 370 liters, the internal temperature is 80 C and it uses a thermostatic valve to blend the output, so the "hot water capacity" is more like 500 liters.
The tl;dw is that it is significantly slower than a resistive or gas-powered water heater, and lowers the temperature of the room by a few degrees, but nothing major. You have to over-provision them compared to your needs. And they are way bigger.
[1]: https://youtu.be/F_7B2shTPPU
This was TC being a weirdo. He bought a 120V hot water heater. Had he done a regular 240V water heater the recovery time would be comparable to pure resistive water heaters.
But the takeaway about cooling is important. These things barely chill the room they are in.
Because heating water requires higher temperature differences (usually heat pumps get more inefficient then). And with an "ordinary" (propane) heat pump you get such high numbers only in summer time (>=20°C) and for water temperatures of max 50°C.