[hash0]

Can someone explain to me in simple terms what the deal is with heat pumps - and why we have not implemented them on a large scale before? It sounds to me like a "reverse refridgerator", so the technology surely has been around for a couple of decades at least?

[throwaway_2626]

It's literally the same technology as a refrigerator.

At least in Europe, much of the current expansion is fueled by the parallel rise of PV solar installs in households (even without subsidies, both combined result in cheaper heating than gas).

[hash0]

So, in essence, it's about heating my appartment using electricity rather than heating water and distributing that around radiators? Let me guess: This has not been very prevalent in Europe because until a couple of years ago, fossil fuels were cheap enough to out-compete electrically generated heat?

[jfengel]

If you wanna get technical, it's about heating your apartment using heat from the outside. Remarkably, it can do that even when it's colder outside than it is in your apartment.

The technical distinction is important, because you get out more heat than you would by just running the electricity into a resistor. And not just by a little: you might get 3x as much heat out.

It's not magic, though it sure seems as if it would be. You really are extracting heat from the outside; the outside gets even colder.

Electricity is involved, but to drive a mechanical motor. It's thermodynamically different from pumping hot water around, where 1 joule of fuel turns into 1 joule of heat. In a heat pump 1 joule of electricity can turn into 3 to 5 joules of heat.

[hash0]

Thank you for that - NOW it's starting to make sense to me. Question remains, though: Why have we not done this before? It seems like the tech has been around for a couple of decades at least, yet I have never heard about heat pumps in this context before last year.

[jfengel]

It's not easy to add a heat pump to an existing building. You can't add it to a radiator system. You need to add a whole air handling system.

The heating system in place was good enough. It used existing infrastructure.

Heat pumps are great for new construction, and they're even more important now that you're adding air conditioning. You didn't need air conditioning nearly as much a couple of decades ago.

Heat pumps are very common in US homes. One advantage is that they run off electricity rather than gas, so you don't need to add a gas hookup to the house. Existing European infrastructure is mostly already rigged for gas, so that's not as big an advantage.

[happymellon]

Exactly.

Even now with 10+ years to break even on the installation it's hard to justify if you think you might move in the next decade.

Here in the UK it would cost £7k-£14k for an air source heat pump, and you'd get between £200-300 reduction on your bills.

If you are moving from a fossil fuel heat source, rather than electricity, then you do get a £7.5k grant. But if not, fuck you.