Heat pump in a large detached
Big bills mean big absolute differences, in both directions. Getting it wrong here is expensive; getting it right saves more than anywhere else.
With the radiators as they are
Saves £32
a year · existing radiators, average size
With upgraded radiators
Saves £291
a year · SCOP 3.4
What to do first
Worth paying for a proper room-by-room heat loss survey rather than a rule-of-thumb quote. The difference between a good and bad design is hundreds of pounds a year.
Upgrading the radiators is worth about £259 a year in this house — which is the difference between a heat pump being a good idea and a questionable one.
The numbers behind that
- Typical gas use for this kind of house: about 23,000 kWh a year.
- That is roughly 19,550 kWh of actual heat, once boiler losses are taken off.
- A heat pump on the existing radiators would use about 6,741 kWh of electricity to deliver it.
- Break-even electricity price: 26.58p per kWh. The cap is currently 26.11p.
If your break-even price is above the price you actually pay, the heat pump wins. If it is below, it does not — and no amount of enthusiasm changes that arithmetic. A dedicated heat pump tariff can move your real price down enough to flip it.