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Heat pump running costs – what has actually worked for you?

 
Air Source Heat Pumps (ASHPs)
Last Post by bobflux 2 months ago
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 kellymcdart
(@kellymcdart)
New Member Member
Joined: 2 months ago
Posts: 1
Topic starter 07/08/2026 10:15 am   [#3130]

Hi everyone,

I’m still trying to get my head around heat pumps and how much difference the settings really make to running costs. There seems to be quite a lot of conflicting advice, especially around flow temperature, weather compensation and whether it’s better to let the system run steadily rather than turning it down for parts of the day.

For those who have had an air source heat pump for a while, what changes have made the biggest difference to your electricity usage?

I’m particularly interested in real-world experience rather than manufacturer figures. Things like changing the flow temperature, adjusting the heating curve, improving insulation, or changing the heating schedule.

Also, has anyone found that a small change in settings made a surprisingly big difference to comfort or efficiency?

Would be really interested to hear what has worked (or not worked) for other owners.



   
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JamesPa
 JamesPa
(@jamespa)
Illustrious Member Moderator
Joined: 4 years ago
Posts: 5499
07/08/2026 3:36 pm  

For me it is a case of keep it simple and follow the 'general' advice.  On 24x7, weather compensation adjusted to min possible consistent with heating the house, active TRV on only 1 radiator (as a courtesy to guests) plus one fancoil, otherwise normal radiators balanced on the LSVs.  Whole house heated with upstairs a bit cooler than downstairs.  I haven't changed much other than swapping from 'active' mode (which tweaks the system according to measured room temperature as well as using weather compensation) to pure weather compensation without room influence, the latter being more comfortable in my house.   

Basically its the classic open loop setup controlled by outside temperature alone.  The only exception to this is right at the end of the season where I switch back to active mode to help combat excess daytime solar gain.

20% cheaper than gas the first year, about the same/a bit less than gas the second year, because of less generous electricity tariff.  In both cases I am ignoring completely the beneficial effect of my solar panels (which in the shoulder season contribute somewhat and I have no battery. 

I have now lost interest in doing the comparison with gas, its about the same or cheaper and much more comfortable.  If I were to get a battery (which I will once plug in is available) it would consistently be cheaper and this winter, given the change is gas/electricity price ratio caused by the war and government policy changes, its likely to be quite a bit cheaper anyway this coming season.

 


4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.


   
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bobflux
 bobflux
(@bobflux)
Reputable Member Member
Joined: 8 months ago
Posts: 187
07/08/2026 7:46 pm  

I installed the air source heat pump in January 2026, it replaced a dead ground source heat pump.

I did not use it in the way the forum recommends: since the installation was setup for an on/off, non inverter, ground source heat pump controlled by a thermostat, I plugged it in, set it up to do exactly that and called it a day.

Fortunately the installation is low temperature underfloor heating. Before insulating the house (it had no insulation at all) worst case flow temperature was 30-35°C but the old heat pump ran quite a lot of hours on cold days... After insulating the hell out of the house, flow temperature got set to fixed 26°C and the thermostat ran the heat pump between 4 and 12 hours every day depending on weather... 

With such low flow temp, COP is ridiculously high and the electric bill is tiny.

Ironically, the heat pump's control algorithm has trouble regulating at such low temperatures. Sometimes it overshoots then oscillates. So, next winter I will configure it properly with weather compensation etc. I don't intend to run it 24/7 because I have lots of PV, so it makes sense to use the free electricity during the day and turn off the heat pump at night. The house has 50cm thick stone walls with exterior insulation, thermal mass is enormous, so there's no issue.

I also used it to send chilled water into the UFH for cooling this summer.

 



   
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