| Topic | Source | What it provides |
|---|---|---|
| Efficiency rule of thumb | DESNZ, Heat pumps explained (28 March 2024) | Around 3 units of heat per unit of electricity; space and radiator points |
| Field efficiency | Energy Systems Catapult, Electrification of Heat | 742 heat pumps; interim median air source SPF 2.80; property types |
| Energy prices | Ofgem, price cap unit rates and standing charges | Cap rates for October to December 2026 |
| Typical use | Ofgem, typical domestic consumption values decision | Low, medium and high consumption from July 2026 |
| VAT | GOV.UK, VAT on fuel and power (Notice 701/19) | Zero rate on domestic electricity to 30 June 2027 |
| Fuel replaced | DESNZ, Boiler Upgrade Scheme statistics | Share of grant-funded heat pumps by previous fuel |
| How homes are heated | ONS, Census 2021 | Households by heating type, England and Wales |
| Grant points | GOV.UK, Boiler Upgrade Scheme: what you can get | Air-to-air amount; hybrids excluded |
| Scotland | Home Energy Scotland, grants and loans | Grant, loan and eligibility for heat pumps |
| Installers | MCS, Find an installer | The register of certified installers |
How the cost figures are worked out
The price of a unit of heat is the fuel's unit rate divided by the heating system's efficiency. Heat pump efficiencies on this site are seasonal figures (2.5, 2.8, 3.0 and 3.5, with 2.8 as the default because it matches the field trial's interim median); boiler efficiencies of 85% and 90% are labelled as assumptions. Standing charges are left out of the per-unit figures and discussed separately, because they do not depend on how much heat you use.
Field data and its limits
The field efficiency figure is an interim median from a large British trial, measured at a stated boundary. It is a middle value, not a promise: half the systems measured did better and half did worse. We use it as a sensible default and say so wherever it appears.
When figures change
Energy prices change every quarter, VAT arrangements can change at a Budget, and statistics are updated monthly. Each page shows the date it was checked. If a source now says something different, the source is right; please tell us through the form so the page can be corrected.