Optional: start from your energy certificate
Enter your postcode to pre-fill your home's details from its certificate. Or skip this and fill the form in by hand.
Your home
How the numbers are worked out
- Wall, roof and floor areas come from the floor area, built form and number of storeys, using storeys about 2.4 m high plus 0.25 m between floors. Where an energy certificate has its own floor measurements we use those instead.
- Window area follows the RdSAP default for the age band and type of home (about 12 to 14% of the floor area plus a constant), and we show it so you can change it.
- U-values come from the UK RdSAP 10 and SAP default tables by age band, wall type, insulation depth and glazing type, with floors worked out using the BS EN ISO 13370 method.
- Heat loss for each element is area × U-value (watts per degree). Ventilation loss is 0.33 × air changes per hour × the volume of the home. A default allowance covers thermal bridging.
- Annual heat is total heat loss × 24 hours × degree days (2,200 for the North West) ÷ 1,000. Fuel is that divided by your heating efficiency, costed at the Ofgem price cap unit rate shown on the page, without standing charges.
This is an indicative estimate to compare options, not an energy performance certificate or a heat pump design. Real homes differ. Bills depend on how you heat the home, the weather and your tariff.
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