Before You Buy
What homeowners need to know about insulation, flow temperature and heat pumps.
A heat pump performs best when your home loses less heat. Improving loft insulation, cavity wall insulation and other energy-efficiency measures can cut heating demand and reduce heat pump running costs. However, you do not always need to fully insulate your home first. Your installer should assess existing insulation and include heat loss in the system design.
For example, current Boiler Upgrade Scheme rules require a valid EPC with no outstanding recommendations for cavity wall or loft insulation. An exception applies where you can show that the work is not possible.
A heat pump usually heats radiators at lower flow temperatures, often around 35–45°C. Gas boilers commonly run at higher temperatures. As a result, some existing radiators may not deliver enough heat for a heat pump.
Larger or higher-output radiators can improve heat transfer and support more efficient operation. Before installation, your installer should calculate room-by-room heat loss. They can then size the heat pump and radiators correctly for each room.
Your heat pump running cost depends on system efficiency, electricity prices and performance in your home. At Ofgem’s current electricity price-cap rate of 26.11p/kWh for 1 July–30 September 2026, a system with a coefficient of performance (CoP) of 3 would use about 8.7p of electricity for each unit of heat produced.
Gas at 7.33p/kWh with a 90% efficient boiler costs about 8.1p per unit of heat. This is why heat pump tariffs, time-of-use electricity tariffs and high system efficiency can make a major difference.
The Boiler Upgrade Scheme (BUS) offers grants for eligible installations in England and Wales. The standard grant is currently £7,500 for air-to-water and ground source heat pumps. Eligible off-gas-grid properties replacing oil or LPG heating can receive up to £9,000 from 21 July 2026.
This can cut the upfront price substantially. It can also change the overall financial case for a homeowner considering a heat pump.
Installing a heat pump involves more than replacing a boiler. Your installer may need to change radiators, pipework, hot water storage and electrical connections. The work can therefore cause more disruption than a standard boiler replacement.
Plan ahead and ask how long the installation will take. Also check whether heating and hot water will be unavailable. Finally, ask what temporary arrangements the installer will provide while the work takes place.