Heat Pump Running Cost Calculator vs Gas Boiler
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Whether a heat pump is cheaper to run than your gas boiler comes down to one comparison: the price of a unit of electricity divided by the heat pump's efficiency, against the price of a unit of gas divided by your boiler's efficiency. Electricity costs more per unit, but a heat pump delivers three to four times more heat per unit than a boiler does. This calculator does that comparison with your numbers.
Note: A negative result means the heat pump is cheaper to run. This compares running costs only — it excludes installation cost, grants such as the UK Boiler Upgrade Scheme, and maintenance. A well-designed system running at low flow temperatures achieves a higher SCOP and shifts the result in the heat pump's favour.
How this calculator works
Both appliances have to deliver the same amount of heat to your home, so the calculator starts from your annual heat demand in kilowatt-hours. For the heat pump, it divides that demand by the SCOP — a SCOP of 3.2 means the unit produces 3.2 kWh of heat for every 1 kWh of electricity — then multiplies the electricity consumed by your unit rate. For the boiler, it divides demand by the boiler's efficiency, since a boiler always burns more gas than the heat it delivers, and multiplies by the gas rate. Subtracting one from the other gives the annual difference.
Worked example
A home needing 12,000 kWh of heat a year with a SCOP of 3.2 uses 3,750 kWh of electricity, costing about £919 at 24.5p. The same home with an 85% efficient gas boiler burns 14,118 kWh of gas, costing about £875 at 6.2p. The heat pump costs roughly £44 more a year — close to parity. Improve the SCOP to 4.0 with a well-designed low-temperature system and the heat pump cost falls to about £735, making it around £140 a year cheaper.
Frequently asked questions
What is SCOP and what is a realistic figure?
SCOP is the seasonal coefficient of performance — the average heat produced per unit of electricity across a whole heating season. Real-world UK installations typically achieve 2.8 to 3.5, with well-designed systems using large radiators or underfloor heating reaching 4.0 or more. Manufacturer headline figures are measured under ideal conditions, so be a little conservative.
Why is a heat pump not obviously cheaper?
Because electricity currently costs roughly four times as much as gas per kilowatt-hour in the UK. A heat pump's three-to-four-fold efficiency advantage roughly cancels that out, which is why the comparison often lands near parity. The result swings on your SCOP and the gap between your two unit rates.
Where do I find my annual heat demand?
Take your annual gas consumption in kWh from your bill, subtract roughly 2,000 to 3,000 kWh if you also cook with gas and heat water, then multiply by your boiler efficiency to get the actual heat delivered. For a typical three-bedroom UK home, 10,000 to 15,000 kWh is the usual range.
Do heat pump tariffs change the answer?
Significantly. Several suppliers offer heat-pump-specific tariffs with reduced electricity rates, or time-of-use tariffs that let you heat more cheaply overnight. Entering a lower effective electricity rate can move the comparison firmly in the heat pump's favour.
What about installation cost and grants?
This calculator deliberately covers running costs only. Installation is typically £8,000 to £14,000 in the UK before support, and the Boiler Upgrade Scheme grant offsets a large part of that. Compare the grant-adjusted installation cost against the annual running-cost difference to judge the full picture.
Does a heat pump work in an old or poorly insulated house?
Yes, but less efficiently. Heat pumps perform best at low flow temperatures, which needs adequate heat emitter sizing — bigger radiators or underfloor heating. In a poorly insulated home the system runs hotter, the SCOP drops, and running costs rise. Insulation improvements usually pay off before the heat pump does.