Heat Pump Cost Calculator

How running costs are calculated

Gas boiler annual fuel cost = Annual heat demand ÷ Boiler efficiency × Gas unit price. A boiler with 88% efficiency delivering 12,000 kWh of heat per year consumes approximately 13,636 kWh of gas.

Heat pump annual electricity cost = Annual heat demand ÷ Seasonal COP × Electricity unit price. A heat pump with a seasonal COP of 3.0 delivering 12,000 kWh of heat consumes 4,000 kWh of electricity.

Standing charges are added separately. The gas standing charge is included in the full gas boiler cost. When a household already pays an electricity standing charge (which is common), switching from gas to a heat pump removes the gas standing charge as an ongoing cost.

Understanding seasonal COP

The Coefficient of Performance (COP) is the ratio of heat output to electrical input. A COP of 3.0 means the heat pump delivers 3 kWh of heat for every 1 kWh of electricity consumed. The seasonal COP (SCOP) averages performance across a full heating season, including cold weather when efficiency drops.

Modern air-source heat pumps have SCOPs typically ranging from 2.5 to 3.5 in UK climates. Ground-source heat pumps have higher SCOPs of 3.5 to 4.5 due to more stable ground temperatures. The higher the SCOP, the lower the running cost.

Break-even electricity price

Because electricity is more expensive per kWh than gas, the heat pump running cost advantage depends on the electricity-to-gas price ratio. The break-even electricity price is the rate at which the heat pump annual cost equals the gas boiler annual cost.

If your electricity price is below the break-even price, the heat pump is cheaper to run. If it is above, the gas boiler is cheaper despite using more fuel. This is why tariffs like Octopus Cosy or Economy 7 can make heat pumps more competitive for homes that can time their heating load.