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Comment by simonblack | Hacker News Reader

Ditto Australia.

We've been using 'reverse-cycle air-conditioners' for heating in Australia for decades. I'm puzzled as to why there is any debate at all on their use for heating. A heat-pump is far more efficient for obtaining heat than direct resistive heating using electricity.

Many houses here use no other form of heating at all. And then at the press of a button, we get cooling in summer too. What's not to like?

* I also have a heat-pump condensing clothes dryer. The overall heat thrown out into the room is extremely low. The hot-air comes out the hot-side of the heat-pump to dry the clothes. The warm-moist air then passes over the cold coils, condensing out the water from the clothes and returning the heat to the cold-side of the heat pump which then pushes that heat-energy out the hot-side, producing more hot air to complete the cycle. I've had this Miele heat-pump condensing dryer going strong since 2009 - 14 years.

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I've seen heat-pump base water heaters, but never a clothes drier. That sounds interesting. Now I have something new to research, thanks! Personally, I'm always curious why there isn't a more unified heat-exchanger system built into the structure of a house. HVAC, Water, Refrigerator, they all need to move heat from one place to another, why not work together?

I've tried to make the idea work in my head many times but my conclusion has been that I don't think there's quite enough co-incident demand for heating and cooling in the average house. For example, yes, I could generate all my domestic hot water from heat from air conditioning in summer, but in winter I need to be able to generate it plus heat the house, so I need enough capacity to generate that heat from the outside air when I'm not using air conditioning (so I don't save on not needing as much capacity), and the efficiency gains probably aren't worth the extra complexity.

For applications like commercial buildings, public swimming pools, industrial sites, etc. can (and increasingly do) definitely benefit from that kind of combination though.

I think the big issue is the different "tuning" for each heat pump system. For example, a heat pump water heater needs a different maximum temperature than an air conditioner, and has much different cycling behavior. This leads to very different design decisions, including refrigerant choice, pressure, compressor type, whether the refrigerant loop is even serviceable, etc. (Some appliances operate at a refrigerant pressure so high that they require being fully assembled at the factory, which would be a non-starter for a manifold system like we're discussing.)

I think this might eventually become a thing once science gets us far enough that there's an "obvious" refrigerant choice for most applications, but we definitely aren't there yet. There are hundreds of different kinds that perform better or worse in different applications.

AFAIK all of the big commercial systems that do multiple different types of heat transfer use water to do it, thus bypassing the entire refrigerant selection issue. Right now the most advanced we can do is VRF ("Variable Refrigerant Flow") systems that can individually select air handlers for cooling or heating (i.e. move the heat from one room to another). These are still commercial units and not really available for residential installs.

There’s a reason new houses get built with geo based heat pumps in Finland.

This enables your hot water heater to use the same circuit to heat water - that decreases your hot water bill to around a third, even in winter as the necessary heat isn’t taken from the indoor air but from the ground.

Yeah, as a Kiwi, watching all the debate happening here is just super weird.

Meanwhile, I'm annoyed that heat pumps that dump the waste heat into the hot water cylinder aren't standard.

It's just the Yanks that have subsidised natural gas in many states, and a messed up energy infrastructure that gives electricity prices in the same range as what we have in Europe while being at war.

I was trying to find heat pump adoption rates for Europe and US.

Seems like its still pretty low in Europe outside some northern countries. Germany is less than 2000/100000 people.

https://www.theecoexperts.co.uk/heat-pumps/top-countries

Meanwhile this link says US has a 15% adoption rate across all income groups. That seems higher than I expected.

https://energypost.eu/u-s-heat-pump-adoption-is-evenly-sprea...

Is there a better source on heat pump adoption rate in Europe and US?

Not a source, but it's more common to have heat pumps in the southern States where winters aren't that bad. I'm born and raised in Arizona and they seemed to be common in houses after the 1973 energy crisis. My grandparents house in Tempe, AZ (was built in like 1950's) did no have one. A house I purchased in central North Carolina had a heat pump. I'm now around Washington DC area in Virginia, and we has gas. I think a simple explanation is that natural gas is almost a by product (certainly from landfills, which is how most USA disposes of trash) and is very cost efficient. Also the energy crisis changed the outlook of house building. I hope that helps explain it some, sorry I don't have any concrete facts I'm typing on a small keyboard.

Yes. Although I have noticed that some people here in Australia go from the belief that "air conditioners use a lot of electricity" so therefore have the misconception a (resistive) electric heater must be cheaper to use than the reverse cycle AC (heat pump). So there is a bit of an education gap even here where they are quite ubiquitous!

I also do want to get a heat pump dryer (it's next on the list after my recently installed heat pumper hot water system), but I don't have quite enough space in the laundry and apart from two or three wet weeks a year I'd mostly only use it to fluff up towels (which is why I don't have a dryer at all at the moment)...

> have the misconception a (resistive) electric heater must be cheaper to use than the reverse cycle AC

You'd think costs would educate. Do people not talk about living expenses much?

Electrical bills come every three months. ALL electricity use is lumped together. So it's a bit hard to disect out what each usage-type is costing, unless you use one of those meters and study up average use over a period. Even then, some things like water heating and even aircons, are directly wired into the mains switchboard, so you would need an electrician to separate out those circuits for measuring. So it just doesn't happen.

Heat pump dryer system is state of the art for efficiency. I saw some complains by American that it takes too long time for drying, but I don't know why they need to dry things so frequently.

If I’m doing 3 loads of laundry for the family, I don’t want a 2.5-3 hour dry cycle to make laundry take all day (or make me do laundry of half the days of the week).

I don’t want a 2.5-3 hour dry cycle

??? That's excessively long. Our heat-pump dryer takes about 20-30 minutes to do one of our loads.* The dryer invariably ends up waiting for the washer to finish.

* Our loads aren't excessively tight in the machine. You have to allow room for the clothes to tumble loosely thus allowing lots of surface area for evaporation.

I quickly googled for “how long does a heat pump dryer cycle take” and got several answers in the 2.5-3 hour range, which is long enough to provoke complaints.

Obviously, if every heat pump dryer took 20-30 minutes, you would not hear complaints about that (that’s much faster than my gas dryer).

Power-input. US dryers would typically work on 110 volts mains. Those similar dryers in the EU or Australia are working on 220 volts mains. Took me a while to click on why the great differences in working-times. 15 amps wiring in the US means 1650 watts, the same wiring in EU is 3300 watts.

That's not it. Electric dryers in the US are overwhelmingly 240V and on a 30A breaker. At 80% of rated, that's 5.7kW available. (Gas dryers here are typically on a 120V, 15A circuit.)

Every heat pump dryer I looked at on the home center's website is 240V. (Edit: I found one Miele on another home center that was a 15A@120V.)

I like mine, but it has a small capacity compared to a standard dryer, and we find that over time water slowly condenses inside of it, so we have to drain it a couple times a year to stop it from shorting its control panel. Not 100% if it's design flaw, micro leak, or what. 8 or 9 year old LG unit I think.

I was thinking about this anomaly yesterday. Then I remembered that most US electrical outlets are at 110 Volts instead of the more usual world-wide standard of 220 volts. So most stuff in the US is under-powered by EU or Australian standards. Being under-powered, it would take longer to dry your clothes.

(That's also why they don't seem to use electric kettles in the US commonly as is normal in 220 volt countries)

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