What does a heat pump actually cost to run in a UK home?

The Coefficient of Performance on a manufacturer's data sheet is a laboratory figure measured at mild outdoor temperatures and low flow. The Seasonal Coefficient of Performance is the same machine averaged across a real British heating season, and it is the number that actually drives your bill. Well-designed UK installs land between 3.2 and 4.8; a retrofit into a warm well-insulated house sits comfortably in the middle of that range.

Every whole point of SCOP is roughly a thirty per cent swing in your annual electricity use for heating. Ask the installer to state the designed SCOP in the quote and to record the commissioned SCOP after handover.

The Ofgem default cap sets the reference electricity unit rate for standard variable tariffs. A heat pump on that tariff typically breaks even with a modern condensing boiler across the year in a well-insulated home. Move the same pump to a heat-pump-specific tariff and it shifts most of its work into the discounted windows; that is where the twenty to thirty per cent saving comes from.

Decide the tariff before the install, not after. Some tariffs require a specific commissioning check or a smart meter class; retrofitting to them after the fact is a common source of avoidable frustration.

Most disappointing running-cost stories collapse into one of two causes: the emitters were left as the boiler had them, so the pump had to run hot; or the hot-water cylinder was scheduled to reheat on peak-rate electricity. Both are controller and design decisions, not faults of the unit. Both are fixable without changing the pump.