Air Source Heat Pump Buying Guide

What Is an Air Source Heat Pump?

An air source heat pump (ASHP) extracts heat from the outdoor air and uses a refrigerant cycle to amplify that heat and distribute it around your home via radiators or underfloor heating. Remarkably, they work even when outdoor temperatures drop below freezing.

How Efficient Are They?

Efficiency is measured as the Coefficient of Performance (COP). A COP of 3.0 means you get 3 units of heat for every 1 unit of electricity consumed. Modern ASHPs typically achieve a COP of 2.5–4.5 depending on outdoor temperature and system design — far more efficient than any gas or oil boiler.

Is My Home Suitable?

ASHPs work best in well-insulated properties. Before installation, an MCS-certified engineer should carry out a full heat loss survey. Key suitability factors include:

**Insulation:** Loft and cavity wall insulation significantly improves performance

**Outdoor space:** The unit needs clear space outside — typically 1m clearance around it

**Radiator sizing:** ASHPs operate at lower flow temperatures (35–55°C vs 70°C for gas). Existing radiators may need upsizing, or underfloor heating is ideal

**Hot water cylinder:** Unlike a combi boiler, an ASHP requires a hot water cylinder

Costs

Installation typically costs £8,000–£15,000 before grants. The government's Boiler Upgrade Scheme (BUS) provides a £7,500 grant, significantly reducing the outlay. MCS-certified installers like Halo Heating can apply for this grant on your behalf.

Running costs depend on your electricity tariff. With an Economy 7 or heat pump-specific tariff, running costs can be comparable to or lower than gas, especially as electricity grids decarbonise.

Planning Permission

Most residential ASHP installations fall under Permitted Development and do not require planning permission, provided they meet size and noise criteria. We handle all relevant checks for you.

What to Look For in an Installer

MCS certification (mandatory for BUS grant applications)

Full heat loss survey before quoting

Transparent cost breakdown

Experience with your property type

Halo Heating is MCS certified and has installed heat pumps across Surrey. Call 01483 676108 for a free heat pump survey.