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, a damp heating season, 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.
Checks before getting quotes
Ask for a room-by-room heat loss survey, a radiator or emitter schedule, expected design flow temperature, hot water plan, controls explanation, and a clear breakdown of any grant assumptions.
If the property is older or off the gas grid, fabric upgrades and oil tank condition can materially change the decision. If the property has mains gas, the electricity-to-gas price relationship and expected SCOP are especially important.