Unfortunately, there is a lot of misinformation about heat pumps, no doubt promoted by lobby groups, and not helped by Energy Secretary Kwasi Kwarteng recently saying (or "admitting" if you read the Mail or Telegraph) that they are not as effective as gas boilers.I suggested the following Fully Charged interviews for a better informed view. https://www.youtube.com/watch?v=a63HkWetENkhttps://www.youtube.com/watch?v=-r6L9HPJfnEHeat pumps are inherently substantially more efficient than gas, and are not new technology (the technology is basically refrigeration technology, well over a hundred years old, and is extremely reliable – when did your fridge ever go wrong?)Gas costs about 4p per effective kw. Electricity costs between 4p (night rate) and 15p - 20p (day rate) - so, say an average of 12p. A modern gas boiler is theoretically 90% efficient, but in practice more like 80%. So, gas heating effectively costs 5p per kw heat. Heating a home with a bar heater is 100% effective (so 1 kw electricity = 1 kw heat). So, simply using electricity to heat a home and for hot water would be about two and a half times as expensive as gas.But, a relatively inefficient heat pump will generate 3 kw of heat for every 1kw of electricity (the "COP"). This reduces the effective cost of power to around the same cost per kw heat as for gas. But an efficient heat pump will work at COP of 5 or more, i.e. 5kw of heat for every 1 kw of electricity. This reduces the cost of power to the same, or lower than the cost of gas (in practice – generally to around the same or slightly lower). It does this by using the electricity to extract the heat from the air, ground or water, then "upgrade" the heat by compressions the volume. (Imagine a basketball full of heat, compressed down to the size of tennis ball - the same amount of energy (heat), but in a smaller area will be much hotter).So the cost of heating with a heat pump falls to or below the cost of heating with gas (and saves the planet).So where to heat pumps go wrong?1 They are more expensive. E.g. our system cost £40k, compared with gas system that would have cost say £15k. The RHI grant pays us back £27k over 7 years. Which is fantastic. If you have £40k to spend up front (which many people do not). £15k - £20k, with perhaps £10k - £15k grant is probably realistic for an average sized house.2 A heat pump is very efficient when upgrading heat from say 8 degrees (ambient ground or air on a cold day) to say 40 degrees, but becomes less efficient the greater the upgrade. So they work best of all in a well-insulated house with a large heating area (such as underfloor heating) which can be heated with heat at say 40 degrees to 50 degrees C, but become less efficient if they have to upgrade the heat to say "delta 60" (an uplift of 60 degrees), and the COP (i.e. multiple of energy output to energy input - so efficiency) will reduce. This is why you need larger radiators – to give of the same amount of total heat, but at a lower temperature so requiring a larger area.3 In the early stages, many heat pumps were badly specified and installed, either by central heating engineers who did not understand the different way heat pumps work , or by people jumping on the government grants’ band wagon. This gave the technology a bad name.4 A typical example of this is installing a heat pump that is too high capacity, so it switches on and off all the time (very energy inefficient). Smaller is often better. Heat pumps do work. We have one, and know many people who also do, all of whom are happy with them.It is a different style of heating a house. A gas boiler can pump out a lot of high level heat (i.e. hot) very quickly (but very inefficiently), whereas heat pumps work best running continuously in the background.At the end of the day, any house will take the same amount of heat to heat. The question is how efficiently that heat can be generated.A good analogy is driving in a car from London to Edinburgh. I can accelerate quickly to a very high speed (e.g. like a gas boiler blast heat at a high level into the house) brake sharply and sit and wait (e.g. then turn the boiler off until the next blast), stop start all the way to Edinburgh. Or I can gradually build up to a slower cruising speed (so the house will take longer to warm up) but then maintain that gentle, constant speed all the way (e.g. keeping the house warm). Either way, I get to Edinburgh at the same time. It is just that I will use far less energy using the "slow and steady" method.
T P Howell ● 1886d