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Hitachi launches CO2 heat pump water heaters with solar-friendly tariff controls

https://www.pv-magazine.com/2026/09/07/hitachi-launches-co2-heat-pump-water-heaters-with-solar-friendly-tariff-controls/
24•thelastgallon•21h ago

Comments

throw0101d•21h ago
CO2 as a refrigerant isn't new:

* 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).

Lwerewolf•31m ago
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.
alex_duf•18m ago
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

PunchyHamster•12m ago
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

moepstar•9m ago
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.

arpinum•8m ago
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.
objektif•35m ago
“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.”

What does this mean?

alex_duf•27m ago
If I'm not mistaken, it means 1kWh of electricity moves 4.1kWh of heat into your hot water tank. Heat pumps are amazing.
PunchyHamster•11m ago
well, in case of water heater it moves it from your room to the water.

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

onedognight•19m ago
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.
elgertam•31m ago
> 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.

Aboutplants•19m ago
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.
_joel•17m ago
I've seen 'tariff' used a fair amount here in the UK on price lists (taxi etc)
koito17•16m ago
The Japanese word used in the context of price lists would be something like 料金表 or 料金メニュー.

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.

myrmidon•5m ago
It's an arab loan word for ~"price list" (originally strongly suggesting an import-duty-like meaning).

The same wort 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).

EspadaV9•13m ago
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.

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152•soheilpro•3h ago•65 comments

Hitachi launches CO2 heat pump water heaters with solar-friendly tariff controls

https://www.pv-magazine.com/2026/09/07/hitachi-launches-co2-heat-pump-water-heaters-with-solar-fr...
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