What does an air source heat pump cost for a 4 bed house?

The headline: £7,000–£13,000 before the grant

For a 4-bedroom house, an air source heat pump installation typically costs £7,000–£13,000 fully installed (estimate, checked October 2026). That is the whole job: the outdoor unit, hot water cylinder, controls, and usually some radiator upgrades.

Then comes the Boiler Upgrade Scheme (BUS): £7,500 off an air source heat pump in England and Wales. Your installer normally applies for it and knocks it straight off your bill, so the net cost for many 4-bed homes lands between £0 and £5,500 (estimate). That grant is the single biggest reason heat pumps have gone from "someday" to "this year" for a lot of households.

What size heat pump does a 4 bed house need?

Usually an 8–12kW unit — but this is genuinely not a bedroom-count decision. The right size comes from a heat-loss survey of your specific house: insulation levels, window sizes, airtightness, and the coldest week of the year. A draughty 1930s 4-bed semi might need 12kW where a modern 4-bed detached manages with 8kW.

Oversizing wastes money and makes the system cycle inefficiently; undersizing leaves you cold in January. Any quote that sizes the unit from a phone call without a survey deserves scepticism. Our heat pump cost calculator gives you a ballpark from your house details, but the survey is what you buy on.

What is included in the price?

A proper quote for a 4-bed should itemise: the heat pump unit itself, a hot water cylinder (heat pumps heat water more slowly, so the cylinder is usually bigger than a boiler-fed one), new controls, and radiator upgrades. This last one surprises people: heat pumps run at lower flow temperatures than boilers (around 35–45°C vs 60–70°C), so radiators often need to be larger — or replaced with underfloor heating — to deliver the same warmth.

Many installers bundle radiator work into the headline price; some list it separately at £1,500–£3,000 (estimate). Always ask which it is before comparing quotes. Electrical upgrades (a dedicated circuit from the consumer unit) and the concrete base for the outdoor unit are usually included too.

What does it cost to run?

At the October 2026 price cap — electricity 26.32p/kWh, gas 7.97p/kWh — a heat pump with a seasonal efficiency (SCOP) of 3.0 produces each unit of heat for about 8.8p. A 90%-efficient gas boiler produces it for about 8.9p. In other words: roughly the same running cost as gas, before you count the grant.

The heat pump pulls ahead if your SCOP is higher (well-designed systems hit 3.5+), if you are displacing oil or LPG (far pricier than mains gas), or if you pair it with solar panels so some of its electricity is home-grown. It loses if the system is badly designed — SCOPs under 2.5 exist, and they are expensive to run. Design quality is everything, which is why the cheapest quote is rarely the cheapest system. See the full heat pump vs boiler running-cost comparison.

Is your 4-bed suitable?

Three checks: insulation first — a heat pump in a poorly insulated house needs a bigger, pricier unit and costs more to run, so loft and cavity wall insulation usually pay for themselves first; outside space — the unit sits outside, roughly the size of a large fridge-freezer, needing airflow and not too close to neighbours (noise regs apply); and your current system — replacing an old boiler at end of life is the natural moment, rather than scrapping a two-year-old boiler.

What the survey might flag up

The heat pump unit is only part of the bill. A proper survey for a 4-bed will usually recommend larger radiators (heat pumps run cooler than boilers, so radiators need more surface area — budget roughly £1,500–£3,000 extra for a full set, estimate), a hot water cylinder if you currently have a combi with no tank, and sometimes pipework upgrades to 28mm or microbore replacement.

Placement matters too: the outdoor unit needs airflow and sits against an outside wall, and installers will check noise at neighbouring windows and the distance to boundaries. None of this is a dealbreaker — it's exactly what the survey is for — but a quote that skips the survey and the radiator question is a quote to be suspicious of.

FAQs

How much does an air source heat pump cost for a 4 bed house?

Typically £7,000–£13,000 installed before grants (estimate, October 2026). After the £7,500 BUS grant, most 4-bed homes pay £0–£5,500 net.

What size heat pump for a 4 bed house?

Usually 8–12kW, fixed by a heat-loss survey — not by bedroom count. Insulation level is the biggest variable.

Is the £7,500 heat pump grant still available?

Yes, in England and Wales under the Boiler Upgrade Scheme (checked October 2026). Installers normally handle the application and deduct it from your bill.

Are heat pumps cheaper to run than gas boilers?

About the same at October 2026 prices for a well-designed system (SCOP 3.0). They win clearly against oil/LPG and when paired with solar.

Will I need new radiators?

Usually yes, or larger ones — heat pumps run cooler than boilers. Most quotes include this; check before comparing.