Heat pump with no (electrical) running cost?

[gareth evans]

What is the real URL?

[David Wade]

I have 4 air-2-air (i.e. AirCon) units. My wife loves them. They produce heat quickly, and distribute it evenly round the room.

Dave

[The Natural Philosopher]

Well yes, if the house is very small and the elecetricity bill is very large

[The Natural Philosopher]

I looked into it here, Tim and it would have needed three phase power and cost £20k plus.

Currently oil is in fact the cheapest heating option you can get.

[Smolley]

That is the only URL.

[gareth evans]

It looks suspicious and best avoided

[Theo]

120sqm, so above average. Total energy consumption (includes all heating, cooking, computers, everything) about 6700 kWh, resulting in an electric bill of about £2200 at current rates. Which is pretty close to the 'average' bill as determined by Ofgem.

Theo

[Robin]

Your total use is well below Ofgem's figures for the price cap: 2,900 kWh of electricity and 12,000 kWh of gas for a "typical" 2-3 bed with 2 people. Even if the gas is only 50% efficient that's equivalent to a total of 8,900 kWh.

[Theo]

Yes, but that's because we're 100% electricity (no mains gas, so gas heating not an option). The bills work out about the same, but we use less energy. The difference is made up by electricity costing more per unit.

Theo

[Robin]

Sorry but I don't see why being 100% electric reduces the total energy need after adjusting for differences in efficiency. ISTM your below-typical usage must reflect differences in your home (eg insulation; location) or lifestyle (eg heating used less often/with thermostat lower).

[Theo]

The heat pump uses 3x less energy that the equivalent gas boiler. Hence the total kWhage is lower. But electricity costs more than gas (currently) so the bill isn't.

Theo

[Robin]

Yes, thanks, me idiot who lost the factor 3 when inserted the 50%.

[Bob Eager]

I see that Gareth still doesn't have a clue...

[gareth evans]

You continue to be a silly abusive infant

[John J]

The real problem with heat pumps is icing up of the external heat exchanger. Many employ a damn great electrical element to thaw off the ice which kicks seven bells out of the overall efficiency. Some split air-conditioning units can be run in reverse so for one used to heat indoors in winter icing can be cleared by switching to cooling mode and melting the ice with heat from indoors. This obviously cools down the room and is undesirable.

[Theo]

I think it's pretty common to just flip direction these days. After all, if you're using your HP to generate water at 40C or more, it doesn't take very much to melt the ice enough for it to fall off (you don't need to fully melt the ice). You likely have enough water in your system that you aren't actively cooling the room (eg if the water were to drop to 35C it's still warmer than the room, just not heating it so much)

Most HPs can also cool (even if that's a setting they don't shout about) so it's basically no extra hardware to reverse direction for defrost.

Theo

[Alex Leon]

Thinking about how the heat pump can work with other applications and how the indoor air quality can increase.