Air Source Heat Pumps in the UK - Complete 2026 Guide

How do air source heat pumps work?

An air source heat pump extracts heat from outside air - even when temperatures are as low as -20°C - and uses it to heat your home and hot water. It works like a refrigerator in reverse: a refrigerant absorbs heat from the air, is compressed (which raises its temperature), and then transfers that heat to your heating system.

For every 1 unit of electricity the pump uses, it typically produces 3-4.5 units of heat. This ratio is measured as the Seasonal Coefficient of Performance (SCOP). A SCOP of 3.5 means 3.5 kWh of heat for every 1 kWh of electricity consumed.

Is my home suitable?

Most UK homes can accommodate an air source heat pump. The key requirements are:

• Outdoor space for the unit (typically 0.5m x 0.5m x 1m - similar to a large fridge)
• A hot water cylinder (most homes with combi boilers will need one adding)
• Some level of insulation (loft and cavity wall recommended, but not essential)
• Radiators sized appropriately (often need upgrading in older properties)

How much does air source installation cost?

Total installed cost before grant: £10,000-18,000. After the £7,500 BUS grant: £2,500-10,500. Typical all-in cost for a 3-bed semi: £11,000-14,000 before grant (£3,500-6,500 after).

The wide price range reflects differences in unit size, installation complexity, whether a hot water cylinder is needed, and local installer rates.

Running costs vs gas boiler

With current Ofgem Q1 2026 tariffs (electricity 24.5p/kWh, gas 6.4p/kWh), running costs are broadly comparable for gas-heated homes on a standard tariff. Oil and LPG users typically save £400-900/year with a heat pump.

The key lever is your electricity tariff. Switching to a heat pump specific time-of-use tariff (Octopus Cosy, Economy 7) cuts the effective electricity rate to 10-15p/kWh during off-peak windows, reducing annual running costs by £400-700 compared to a gas boiler. See full payback period analysis →

R290 vs R32 refrigerant — what you need to know in 2026

Heat pumps use a refrigerant to transfer heat. In 2026, the market is shifting from R32 to R290 (propane). Here is why it matters:

• R290 (propane): Global Warming Potential (GWP) of just 3. Enables higher flow temperatures (75°C+), so fewer radiator upgrades in older homes. Used in Vaillant aroTHERM plus.
• R32: GWP of 675. Still performs excellently. Used in Mitsubishi Ecodan, Daikin Altherma 3, Samsung EHS. Much wider installer availability.

R290 is the more future-proof choice, but R32 models are not going away and still perform excellently. The refrigerant type is one factor to weigh alongside efficiency, noise, installer coverage and price.

Cold weather performance — what happens below 0°C

Modern heat pumps continue to operate efficiently in cold UK winters. Standard models are rated down to -20°C; enhanced models like the Mitsubishi Ecodan HyperCore operate to -28°C. Efficiency (SCOP) does fall as temperatures drop, but current generation units maintain useful output even at -10°C — typical of a cold British night.

Budget models can lose significant capacity below 5°C. When comparing quotes, look for 'cold climate' rated units and check the manufacturer's published COP at -7°C (the standard UK test temperature) alongside the headline figure.