Guide · By property
Heat pump for a 3-bed semi
The most common UK property type. Here's the sizing, install cost and annual bill you can expect.
A typical UK 3-bed semi needs a 7–9 kW air source heat pump, costs £9,500–£12,500 installed before grant (£2,000–£5,000 net after the £7,500 BUS), and runs at around £1,100/year with a SCOP of 4.5.
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Sizing for a 3-bed semi
Heat loss for a 3-bed semi typically lands in the 6–10 kW range depending on age and insulation. Post-2010 builds: 5–7 kW. 1980s–2000s: 7–9 kW. Pre-1945 solid wall: 9–11 kW (insulate before specifying — a 12 kW system in a leaky house costs more to run and more to buy).
Install cost reality
Expect £9,500–£12,500 for an MCS install before grant: outdoor unit, 180–210L cylinder, controls, radiator changes (2–4 radiators), commissioning. After the £7,500 BUS grant most households pay £2,000–£5,000 out of pocket.
Annual bills
A 3-bed semi with 12,000 kWh/year heat demand and a SCOP of 4.5 uses ~2,700 kWh of electricity. At 27p/kWh that's £720 plus standing charges — total around £1,100/year. Roughly the same as a modern gas boiler at current prices.
Frequently asked questions
- What size heat pump for a 3-bed semi?
- Most UK 3-bed semis need a 7–9 kW air source heat pump. A 1930s solid-wall semi will need closer to 9–11 kW; a 2010s new-build sits at 5–7 kW.
- Will my existing radiators work?
- Usually 2–4 of them need uprating to handle the lower flow temperatures heat pumps run at. A heat-loss survey identifies which ones.
- Energy Saving Trust — Heat pump efficiency, running cost and SCOP benchmarks (UK).
- Nesta — How to Heat 28 Million UK Homes — Independent research on heat pump deployment and running costs.
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