It would be interesting to hear from all the heat pump users what seasonal COP (Coefficient of Performance) they think they are achieving. As we've had our heat pump a year now we have done this calculation and we were surprised it was 3.9. We've had some really cold weather here this winter ... with minus temperatures night and day for several days at a time. So the heat pump will have had to work hard. Given that our old oil boiler was probably 85% efficient at best, we are pleased that the heat pump has performed so well.
We too were advised that it is not efficient to keep switching the temperatures up and down all the time.
Bee x
Gardener and beekeeper in beautiful Scottish Borders
A single bee creates just one twelfth of a teaspoon of honey in her lifetime
You'd think there would be less heat to extract when the outside temperature is low, @KT53, but the ASHP still manages to heat this house to 20C even when it's below freezing outside. I think you need someone like @raisingirl to explain the science - it's certainly beyond me. Edited to say: it obviously must take more energy to extract the heat when it's very cold outside, and therefore costs more to run at that time. I know, but don't pretend to understand, that an ASHP typically is 300% efficient...
How can anything be more than 100% efficient? Possibly 3 x more efficient than something else, but what is the 'something else' it's being compared to. Not trying to catch you out @Liriodendron as I don't doubt that's what you were told.
Hi @KT53, the 300% efficiency number comes from the fact that you get so much more energy (heat) out than has gone in (electricity). Environmental Yield and electrical consumption are used to calculate it. (EY+EC)/EC. @Bee witched, agreed, it's not a good idea to frequently change temps. I should say that I only started doing it when the weather got warmer so that the ASHP wouldn't struggle warm up before dawn. When the consultant told us we would set the bedroom to 19 degrees I told him he's havin' a laugh, cos ever since I spent 3 years in South Africa, I cannot tolerate anything below 19. But, something strange happens with a whole house heating system. Because everything is warm - walls, floors, ceilings, furniture, you get a very consistent cosy environment.
I find myself wondering if anyone's invented an air pump system with a "reverse" setting to cool the indoors in summer? I guess that would negate the environmental benefits though.
We all have them - fridges and freezers. It's the same gubbins, just works the other way round.
Billericay - Essex
Knowledge is knowing that a tomato is a fruit. Wisdom is not putting it in a fruit salad.
How can anything be more than 100% efficient? Possibly 3 x more efficient than something else, but what is the 'something else' it's being compared to. Not trying to catch you out @Liriodendron as I don't doubt that's what you were told.
The 'free' energy (heat) from the air isn't counted, only the electricity that it uses, which is what you pay for. It doesn't use electricity to 'make' heat, it uses it to power a compressor. The heat is produced by a vapour compression cycle; a refrigerant is compressed and expanded using the latent heat of evaporation to take 'heat' at 5 to 10C to produce heat at 30 to 40C. When the outside temp is below about 5C the efficiency begins to drop, because the compressor has to work harder, but across a 'normal' winter, we get the sort of average efficiency that Bee suggests - 3.5 to 4 typically. (If your house is very draughty, it'll be worse than that). But even if they are the worst they can ever be - 1 and a bit - they are still more efficient than a gas or oil boiler which is less than 1.
The issue currently is that electricity costs x4 gas, so an efficiency of 4 is basically break even for costs. It won't stay like that. The Government are already looking at ways to change the way the energy network is priced. Electricity will in the medium term inevitably cost relatively less compared to gas, so that multiplier will reduce and the heat pump will start to look like a much better deal.
In about 10 years you won't be able to buy a gas boiler to replace an existing one. It may be sooner than that when there will be a minimum EPC rating required to sell or rent a house. So you may have to embrace the idea.
Gardening on the edge of Exmoor, in Devon
“It's still magic even if you know how it's done.”
@raisingirl I really don't think I will have to 'embrace' heat pumps any more than I will have to embrace buying an electric car. I'm over 70 now so could simply purchase a new gas boiler before they are banned, and buy a second hand internal combustion engined car to see me through until I pop my clogs.
The "gun metal" pipework for the radiators here had to be replaced, but I don't think it was a significantly bigger gauge - just different material. Maybe microbore pipework wouldn't be suitable?
Since 2019 I've lived in east Clare, in the west of Ireland.
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As we've had our heat pump a year now we have done this calculation and we were surprised it was 3.9. We've had some really cold weather here this winter ... with minus temperatures night and day for several days at a time. So the heat pump will have had to work hard. Given that our old oil boiler was probably 85% efficient at best, we are pleased that the heat pump has performed so well.
We too were advised that it is not efficient to keep switching the temperatures up and down all the time.
Bee x
A single bee creates just one twelfth of a teaspoon of honey in her lifetime
How can anything be more than 100% efficient? Possibly 3 x more efficient than something else, but what is the 'something else' it's being compared to. Not trying to catch you out @Liriodendron as I don't doubt that's what you were told.
@Bee witched, agreed, it's not a good idea to frequently change temps. I should say that I only started doing it when the weather got warmer so that the ASHP wouldn't struggle warm up before dawn. When the consultant told us we would set the bedroom to 19 degrees I told him he's havin' a laugh, cos ever since I spent 3 years in South Africa, I cannot tolerate anything below 19. But, something strange happens with a whole house heating system. Because everything is warm - walls, floors, ceilings, furniture, you get a very consistent cosy environment.
It's the same gubbins, just works the other way round.
Billericay - Essex
Knowledge is knowing that a tomato is a fruit.
Wisdom is not putting it in a fruit salad.
The issue currently is that electricity costs x4 gas, so an efficiency of 4 is basically break even for costs. It won't stay like that. The Government are already looking at ways to change the way the energy network is priced. Electricity will in the medium term inevitably cost relatively less compared to gas, so that multiplier will reduce and the heat pump will start to look like a much better deal.
In about 10 years you won't be able to buy a gas boiler to replace an existing one. It may be sooner than that when there will be a minimum EPC rating required to sell or rent a house. So you may have to embrace the idea.
“It's still magic even if you know how it's done.”