Heat Pump Savings Calculator — UK & EU Homes
A heat pump savings calculator compares a heat pump with a gas boiler for a UK or EU home. Enter your yearly heat demand, the heat pump's COP and your electricity and gas prices, and it shows the yearly running cost of each, the saving, and how long the installation takes to pay for itself.
Default tariffs are the Ofgem price cap for 1 October to 31 December 2026 (26.32p electricity, 7.97p gas). The cap changes every three months — enter your actual tariff rates.
How it works
- Enter your yearly heat demand in kWh — a typical UK home needs about 12,000 kWh of heat a year.
- Enter the heat pump's COP (3.0 is typical) and your electricity and gas prices in pence per kWh.
- Enter the installation cost and any grant. See the yearly cost of each system, the saving and the payback time.
Formula
Worked example
A home needs 12,000 kWh of heat a year. With a heat pump at COP 3.0, that takes 4,000 kWh of electricity. At the Ofgem price cap rates for October to December 2026 — 26.32p per kWh for electricity and 7.97p for gas — the heat pump costs £1,052.80 a year, while a gas boiler at 85% efficiency uses 14,118 kWh of gas costing £1,125.18. The heat pump saves £72.38 a year. With a typical £11,000 installation minus the £7,500 Boiler Upgrade Scheme grant, the £3,500 net cost would take about 48 years to pay back at these prices — so check your own tariffs and grant before deciding. Tariffs are illustrative defaults from the Ofgem cap; edit them to match your actual rates.
Frequently asked questions
How much does a heat pump save vs a gas boiler?
It depends on the COP and the electricity-to-gas price ratio. In the example above — COP 3.0 at the October to December 2026 Ofgem cap rates — the heat pump saves £72.38 a year. A higher COP or cheaper electricity saves more; a lower COP can cost more than gas.
What is COP on a heat pump?
COP (coefficient of performance) is the heat delivered for each unit of electricity used. A COP of 3.0 means 3 kWh of heat for every 1 kWh of electricity. Modern air-source heat pumps typically achieve a seasonal COP of 2.5 to 3.5.
What is the Boiler Upgrade Scheme grant?
A £7,500 grant in England and Wales towards the cost of installing an air-source heat pump (and £7,500 for ground-source too). It is claimed by the installer, not the homeowner. Scotland has a separate Home Energy Scotland scheme.
Why is the payback so long in the example?
Because electricity costs about 3.3 times as much as gas per kWh under the current cap, a COP of 3.0 only just beats a gas boiler. The saving is real but small, so the installation cost takes decades to recover unless electricity gets cheaper or gas gets dearer.
What COP should I use?
Use the seasonal COP (SCOP) from the installer's quote for your home, typically 2.5 to 3.5 for a modern air-source heat pump. Well-insulated homes with underfloor heating or large radiators get the best COP.
Are the tariffs in the calculator up to date?
The defaults use the Ofgem price cap for 1 October to 31 December 2026: 26.32p per kWh for electricity and 7.97p for gas. The cap changes every three months, so enter your actual tariff rates for a figure you can rely on.