Overview
Electric boilers work identically to gas boilers — same radiators, same controls — but use an electrical element instead of a gas burner. They're 100% efficient, silent, and need no flue.
Running costs
Gas combi: ~7p/kWh at 92% efficiency = ~7.6p per unit of heat. Electric boiler: ~28p/kWh at 100% efficiency = 28p per unit of heat. Electric is approximately 3.7x more expensive to run.
Annual cost difference
For a 3-bed semi spending £1,100/year on gas: equivalent electric cost would be approximately £4,000/year. That's £2,900 more per year — every year.
Installation
Electric boiler: £900–£1,500 fitted, no flue needed. Gas combi: £999–£1,799, flue required. Similar upfront cost.
When electric makes sense
Off-grid homes where gas, LPG, and oil are all impractical. Very small properties with minimal heating demand. Homes with large solar PV arrays.
Verdict
For any home with gas available, a gas combi is the economically rational choice. The running cost difference is so large it cannot be offset by installation savings or efficiency differences.