United Kingdom

There's an awful lot of information on the internet about heat pumps that's coming out of the States, and is either completely incorrect, irrelevant for the European model, or blatantly anti-progressive propaganda.

Remember their houses are made of cardboard, their plumbing would make an ancient Roman laugh, and they have girly electricity.

Ignore everything you hear from that side of the pond, and you'll find the argument far more one-sided

However heat pumps just don’t seem to make any sense, and the more marketing materials I read critically, the less convinced I am of their practicality, nor the integrity of the vendors - if they work similarly to air conditioning units or refrigerators why do they cost 20x as much as those devices?

A refrigerator cools a fairly small volume with excellent insulation, which allows it to use a fairly small compressor running at a single speed. This is cheap.

The big differences between typical air conditioning units and heat pumps are:

• they're set up to move heat both ways (eg: both heating and cooling) which requires a tiny bit of additional hardware
• They often have a more substantial compressor to handle the larger temperature difference associated with colder temperatures
• They're a lot more likely to be a system intended to support the whole home instead of a single room
• People care about efficiency, which has variable-speed systems getting installed
• There's a lot of demand for them right now, and limited supply

The big reason somebody might want air to water is that it enables a low-cost retrofit of an existing heating system which uses water to distribute heat. Definitely not what I'd choose if designing from scratch, but I can see how it makes financial sense in a lot of homes.

And yes, induction is amazing, but there are a whole bunch of people who have been marketed into treating gas stoves as their personal identity.

why the UK is pushing do hard for air to water is a mystery to me.

I was a little confused when I followed a European forum. The transition to heat pumps has been a big deal, lot of discussion in the UK and Germany. It had a bunch of people talking about boilers and having heat pumps heat water, which confused me. I'd only heard about boilers in the US much in the context of large buildings with old steam heating systems.

In the US, I've seen plenty of air source heat pumps. Some water source heat pumps. But they both are used to heat (or chill) air, which is then blown into ducting and circulated through the house. Provides ventilation and such and humidity control. But it seemed to be overwhelmingly the case that people in Europe were talking about heating water and circulating that.

Small window or through-wall air conditioning units do obviously heat air, usually for one room. Split minis move refrigerant, which ultimately heats or cools air.

And it seems like you'd rather have ducting, as it can provide control over a given ratio of fresh air to an area of a building and filter it.

I was able to find a few companies in the UK dealing with ductwork, but they focused on new office buildings.

I eventually figured out what was going on.

A lot of houses in the US were built after the introduction of air conditioning. Not only that, but the US has more areas that get quite hot than Europe, so once air conditioning was an option, people really wanted it. The result is that a lot of US housing was built with central air conditioning.

This meant that when houses were designed, ductwork was built into the design.

Ducts are relatively-large. It takes a lot of space to move a given amount of heat.

It is not easy to retrofit ducting into an existing house. You have to have this big thing jammed into the house somewhere that runs to all rooms.

Water is much denser. If you use water to move your heat around, you don't require that much space. So if you retrofit an existing house, you don't have to mess the house up. Not only that, but a lot of buildings in the UK had apparently already been set up with systems that heated water with natural gas and then moved it around the building to heat it, so putting in a heat pump could use that existing system.

My guess is that people did the math and decided that it didn't make sense to massively go rip up existing houses when they could stick comparatively-unobtrusive additional water pipe in.

My guess is that what will happen is that new buildings will incorporate ductwork, so there will be a very slow transition to ductwork. But it won't happen overnight, just as buildings age out and are demolished.

The current transition to heat pumps that they're doing is on a much shorter timeline than that.

On the other hand, using a heat pump for replacing a hot water heater is definitely a good thing. Using a heat pump on an old water radiator system may not work well. Friends had to replace a gas heater for their water radiator system and were told that there wasn’t a heat pump unit hot enough for the retrofit.

The air to water thing is huge in the Netherlands too. I think it is because it's the traditional way of heating the house. So people looking to replace it will want the same thing.

It's even so that the word heat pump only is used for the air-water units, not the air-air ones, those are called airconditioners.

We changed to an electric boiler and air heat pumps, and have archived quite the reduction, certainly when the gas price went sky high.

But there is a lot of resistance to the idea.

I’ve been considering getting a multi unit airco (the warms)

For heat pumps I’d need to replace all my radiators

I hate induction with a passion, beep boop it doesn't work because a drop of water, you can't put anything on it, the controls are obnoxious and you have to change at least some cookwear.

I love gas, sure it's more a preference than logic but it's so snappy ! Turn the button and you have 5000watts of heat, no long click this, short click that, and when done, just turn the knob.

Now, it has drawbacks like when it's windy, it does get super hot etc. but I'd get hologen (with knobs) before any induction.

/Rant off

As someone fitting solar to a small boat.

Both is an option. IE have a water tank that can heat water on lower power slowly. Making use of reusable energy. And a heat bump to efficiently use it. (Not really doable on a small boat)

And fit gas (i use electric) instant water heaters at the taps. I have it set up that I can turn it on and often use if when connected to shore power in winter.

But use a tank heated by a solar dump when possible.

Given how cheap solar panels are now. (£69 for 410w panal plus shipping) if your able to fit stuff yourself. It is worth the effort.