What a modern combi actually costs to run in 2026.
Primary question · If I install a new boiler today, what should I realistically expect to pay each winter for the next ten years?
A correctly sized 28 kW combi in a typical British 3-bed, paired with a sensible smart control and weather compensation, runs at roughly £1,200 to £1,700 per heating year at current price-cap gas. The variance between households of similar size is driven less by the boiler itself than by setback strategy, hot-water habits and whether weather compensation is genuinely doing its job.
Anyone trying to forecast a heating bill that holds up across a wet, cold or mild British winter.
Typical 3-bed annual heating: £1,200 to £1,700 in 2026. Add £300 to £500 for hot water on a combi without a cylinder.
- Realistic mid-tariff numbers, not best case
- Captures the control-strategy variance that dwarfs the brand variance
- Honest about hot water as a separate cost
- Households with a heat-pump-ready electricity tariff sit outside these numbers, and the gap is widening
Confirm with your installer that weather compensation is enabled at commissioning and is connected to an external sensor, rather than a switch left in the off position.
The boiler is the small part of the running cost. The thermostat strategy, the flow temperature and whether weather compensation is actually working between them carry the rest of the equation. A mid-range boiler with a competent control bundle reliably beats a flagship that has been wired in for convenience.