Overview
Electric boilers are 100% efficient — every unit of electricity becomes heat. Gas combi boilers are 89–94% efficient. Yet electric boilers have significantly higher running costs for most UK homes. The reason is the price gap between electricity and gas.
Running costs
As of 2025, electricity costs approximately 24p/kWh vs gas at 6p/kWh — a 4x difference. A gas boiler at 93% efficiency is roughly equivalent in running cost to an electric boiler at 23% efficiency (which is impossible). In practice, gas heating is typically 60–70% cheaper to run annually than electric heating.
Annual cost comparison
Average UK home heating cost (gas combi): £800–£1,200/year. Same home with electric boiler: £2,400–£3,600/year. Difference: £1,600–£2,400/year in favour of gas.
Installation cost
Electric boiler: typically £500–£1,000 installed (no flue, no gas pipework). Gas combi: £999–£1,500 installed. Electric wins on installation cost.
When electric boilers make sense
- Off-gas-grid properties where the alternative is expensive oil or LPG
- Very small flats with minimal heating demand
- Properties paired with solar panels (PV offsetting the electricity cost)
- Narrow boats, outbuildings, annexes
Verdict
For any property connected to the gas grid: gas combi is the right choice for the vast majority of homeowners. The running cost difference of £1,600+/year is decisive. Electric boilers only make practical sense in specific off-grid or very low-demand scenarios.