Heat pump in a period cottage
Solid stone or cob walls, often listed, frequently off the gas grid on oil. High heat demand and limited scope to insulate — but oil is expensive enough that the comparison can still favour a heat pump.
With the radiators as they are
Saves £26
a year · existing radiators, on the small side
With upgraded radiators
Saves £357
a year · SCOP 3.4
What to do first
Off-grid on oil is the strongest case for a heat pump in the whole country. Get the running cost compared against oil, not against mains gas.
Upgrading the radiators is worth about £331 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 16,000 kWh a year.
- That is roughly 12,000 kWh of actual heat, once boiler losses are taken off.
- A heat pump on the existing radiators would use about 4,800 kWh of electricity to deliver it.
- Break-even electricity price: 26.64p 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.