External expert review: HeatWise Home does not currently publish named external expert reviewers. We are working toward adding independent review from qualified retrofit, heating, or building-energy professionals. Until then, users should treat our calculators and guides as educational planning tools and confirm decisions with official sources and qualified installers.
Medium confidence
Energy prices, grant rules, and installation costs change frequently. The figures on this page are planning ranges, not quotes. Always confirm your current tariff, delivered fuel price, installer scope, and eligibility in the named references linked below.
Helpful next step
See formulas, assumptions, and limits behind each estimate.
What UK homeowners should know about heat pump sizing
The UK market is shaped by mains gas in many towns and cities, oil or LPG in off-grid homes, and grant rules that can differ by nation. That means heat pump sizing should be assessed using your own bills, installer quote, and current official scheme guidance.
Do not rely on one average installation cost or one national tariff. Electricity, gas, and oil prices change, and a heat pump that performs well in one home can disappoint in another if heat loss, radiators, controls, or hot water design are not handled properly.
Example planning calculation
A common first check is to estimate useful heat demand, then compare current fuel cost with expected heat pump electricity use. For example, a 12,000 kWh heat demand divided by SCOP 3.2 gives about 3,750 kWh of heat pump electricity use.
If electricity costs 30p per kWh, that would be about GBP1,125 per year for heating energy before standing charges. The current system should be compared on useful heat, not just fuel bought, because boiler efficiency matters.
United Kingdom assumptions
Currency: GBP. Electricity: £0.25 per kWh. Gas: £0.06 per kWh. Heating oil: £0.11 per kWh.
Planning ranges: Electricity GBP 0.22-0.34 per kWh (Ofgem regional cap spread and available tariffs); Gas GBP 0.05-0.11 per kWh (Ofgem cap benchmark and regional/tariff variation); Heating oil GBP 0.09-0.13 per kWh equivalent (kerosene supplier tracking, delivery-size and season dependent).
Last checked: 2026-04-28. Confidence: medium.
Sources: Ofgem energy price cap and market data, GOV.UK Boiler Upgrade Scheme, MCS standards and UK building fabric guidance.
Caveat: prices vary by supplier, tariff, region, standing charge, and usage. Electricity/gas benchmarks align with Ofgem's 1 April to 30 June 2026 cap context (24.67p/kWh electricity and 5.74p/kWh gas GB average, Direct Debit) and broader tariff variation. Heating-oil range uses UK supplier-tracked kerosene pricing converted to kWh-equivalent planning values.
This is only a broad planning estimate and is not a replacement for a professional room-by-room heat loss survey.
Suggested next steps
Book a professional heat loss survey before choosing equipment. Ask installers to confirm emitter suitability at lower flow temperatures. Review insulation and draught proofing before final sizing.
Calculators on this site are estimates only. Always get a professional heat loss survey and verify current grant rules, tariffs, and product suitability before making purchase decisions.
Sizing FAQs
Only roughly. Floor area helps provide a starting estimate, but accurate sizing depends on fabric losses, airtightness, ventilation, glazing, and local climate.
Where we suggest a partner, we aim to prioritise relevant, reputable providers or installers. We do not recommend proceeding without checking credentials, quotes, warranties, and official grant requirements.
Helpful next step
Pressure-test savings assumptions before committing to upgrades.