An ASHP is not a direct boiler replacement that works the same way. Understanding how it works differently is key to knowing whether one is right for your home.
What is an air source heat pump?
An air source heat pump (ASHP) extracts heat from outside air — even at temperatures as low as -20°C — and moves it into your home. It does not generate heat by burning fuel. It moves it.
For every 1 kWh of electricity an ASHP uses, it typically delivers 2.5 to 4 kWh of heat. A gas boiler maxes out at around 90% efficiency. A heat pump’s effective efficiency is 250–400%.
Is my home suitable?
This is the most important question. ASHPs work best in well-insulated homes with underfloor heating or oversized radiators, where the heating system runs at lower temperatures. A proper heat loss calculation must be done before any quote is meaningful.
The Boiler Upgrade Scheme
The UK Government’s Boiler Upgrade Scheme (BUS) offers a £7,500 grant toward an ASHP installation. Your installer applies on your behalf. This grant significantly changes the economics and should factor into any comparison with a new gas boiler.
Running costs versus gas
ASHPs run on electricity, which is more expensive per unit than gas. The saving comes from the high efficiency — you use far less electricity than you would gas. Whether you save money depends on your current usage and tariff. On specialist tariffs like Octopus Cosy, savings are more predictable.
How long does installation take?
A standard domestic ASHP installation typically takes 2–3 days. Your installer handles any hot water cylinder changes needed as part of the process.
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