What determines heat-pump running costs at home?

Heat-pump running cost is not a fixed saving: it depends mainly on delivered heat, real seasonal efficiency and the electricity tariff, all shaped by design and operation.

Which three numbers matter most?

Start with the home’s annual heat demand, the system’s seasonal performance and the unit price of electricity. Electricity used is approximately delivered heat divided by seasonal efficiency, with hot water and auxiliary use included appropriately. A quote should disclose rather than hide these assumptions.

How does system design affect cost?

Lower practical flow temperatures, correctly sized emitters, weather compensation and steady control can improve efficiency. Excessive heat loss, poor commissioning, frequent inefficient boosting or unsuitable controls can worsen it. Comfort settings and hot-water use remain household-specific.

How should you compare with the current system?

Use recent bills or fuel deliveries and separate space heating from other uses as carefully as possible. Test more than one tariff and efficiency scenario. Solar or battery storage may change when grid electricity is bought, but neither creates a guaranteed saving or repairs a poor heating design.