The honest picture in 2025
Air source heat pumps (ASHPs) are more energy efficient than gas boilers — a modern ASHP produces 3–4 units of heat for every unit of electricity consumed (COP of 3–4). But energy prices mean this advantage is largely cancelled out for many UK homes in 2025.
Running cost comparison
Gas boiler at 93% efficiency: approximately £900–£1,200/year for an average 3-bed semi. Air source heat pump at COP 3.0: electricity cost approximately £1,100–£1,500/year (at 24p/kWh electricity). The electricity price premium vs gas largely offsets the heat pump's efficiency advantage for many homes.
Where heat pumps run cheaply
Heat pumps perform best in well-insulated homes (EPC A/B), where they can run at lower flow temperatures and achieve higher COP (3.5–4.5). In a poorly insulated older property, COP drops to 2.0–2.5, making running costs significantly higher than gas.
Installation cost
ASHP installation: £8,000–£15,000 (even after BUS grant of £7,500). Gas boiler: £999–£1,500. The capital cost difference is £7,000–£13,000+.
Payback period
At current energy prices, the payback period for an ASHP (vs a new gas boiler) is 15–25+ years in most existing UK homes. For well-insulated new builds, this improves to 8–15 years.
Future-proofing
Gas boilers will eventually be phased out for new installs (current UK policy: no new gas boilers in new builds from 2025, existing homes later). A new gas boiler installed today will likely have a 10–15 year useful life before this becomes pressing.
Verdict
For most UK homes with existing radiators and moderate insulation: a new gas boiler is the right choice in 2025. If you're building new, retrofitting with full insulation, or have EPC A/B: an ASHP is worth serious consideration. We can install gas boilers — and advise honestly on heat pumps when they're the right answer.