Heat Pump Sizing by House Size UK
This is the definitive UK heat pump sizing reference — covering every property type from 1-bed flats to 5+ bed country houses, adjusted for three insulation levels. Use these tables to estimate what you need before getting a proper heat loss survey from an MCS installer. Getting the size right saves money upfront and delivers lower running costs for the system's 20+ year lifespan.
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Complete Sizing Tables by Property Type
| Property | Well-insulated (EPC C+) | Average (EPC D) | Poor (EPC E+) |
|---|---|---|---|
| 1-bed flat | 2-3 kW | 3-4 kW | 4-5 kW |
| 2-bed flat/terrace | 3-5 kW | 4-6 kW | 6-8 kW |
| 2-bed semi | 4-6 kW | 5-7 kW | 7-9 kW |
| 3-bed semi | 6-8 kW | 7-10 kW | 10-13 kW |
| 3-bed detached | 8-10 kW | 9-12 kW | 12-16 kW |
| 4-bed semi | 8-10 kW | 9-12 kW | 12-15 kW |
| 4-bed detached | 10-13 kW | 12-16 kW | 16-20 kW |
| 5-bed detached | 14-18 kW | 18-24 kW | 24-30 kW |
| Bungalow (2-3 bed) | 5-8 kW | 7-10 kW | 10-13 kW |
Indicative ranges only. A proper MCS heat loss survey is mandatory for BUS grant claims.
Watts Per Square Metre Guide
Adjustment Factors
Location: Add 5-10% for northern England and Scotland (colder design temperatures). Exposure: Add 5-10% for exposed/hilltop locations. High ceilings: Add 10-20% for rooms above 2.7m (common in Victorian homes). Hot water: The heat pump must also heat your cylinder — add 2-3 kW for a 200-250L cylinder. Homeowners using solar panels to offset electricity costs do not need a different size but benefit from lower running costs.
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Frequently Asked Questions
How many kW per square metre?
Roughly 50-80 W/m2 well-insulated, 80-120 W/m2 average, 120-160 W/m2 poor insulation.
Does location affect size?
Yes — northern/Scottish locations add 5-10% due to colder design temperatures.
Should it size for hot water too?
Yes — add 2-3 kW for the hot water cylinder.
Is bigger always better?
No. Oversized pumps cost more and cycle inefficiently. Correct sizing from a proper calculation is essential.
Heat pump sizing depends on property type, insulation level, and location. MCS-certified installers use room-by-room calculations mandated by the Boiler Upgrade Scheme. Both air source and ground source systems must be correctly sized. Solar generation offsets running costs without changing sizing.