Heat pump running cost
Against your current gas boiler, at today’s prices. The honest answer depends on your radiators more than anything else.
This matters more than anything else on the page.
Use my own tariff rates
That is close enough to a draw that it would move either way with a tariff change or a mild winter.
Next: what one costs to install after the grant.
Why radiators decide this
Electricity costs about 3.6 times what gas costs per unit. So a heat pump has to be at least that much more efficient than your boiler just to break even. That efficiency is set by how hot the water has to be: small radiators need hot water, hot water means a hard-working heat pump, and a hard-working heat pump is an expensive one.
Underfloor heating runs at around 35°C and gets excellent efficiency. Radiators sized for a heat pump run at 45°C and do well. Existing radiators pushed to 55°C or more do badly. This is why a good installer talks about your radiators before they talk about the unit.
What this does not include
- Hot water, which a heat pump also provides — usually at similar or slightly better cost than gas.
- The standing charge on electricity, which you pay either way.
- Any special heat pump electricity tariff, which can change the answer substantially in the heat pump’s favour.
- Maintenance, which is broadly comparable between the two.
The honest summary
At the current price cap, a heat pump in a well-prepared house saves money. In a house with undersized radiators and no intention of changing them, it may not — and anyone telling you otherwise is probably selling one. That does not make heat pumps bad; it makes radiator sizing the thing to spend your money on first.