How much does an immersion heater cost to run?
A typical immersion heater costs about £1.58 per heat-up to run. At 7 heat-ups a week that is £11.05 a week, or £574.83 a year, based on 3,000 W for 2 hours (6.00 kWh) at 26.32p per kWh.
Adjust for your immersion heater
Worked example
3,000 W is 3 kW. Running for 2 hours uses 3 × 2 = 6.00 kWh. At 26.32p per kWh that costs £1.58.
One two-hour heat-up a day comes to £574.83 a year. Cutting heating time by a quarter, with a timer or a lagging jacket, would save about £143.71 a year.
How to cut the cost
Fit a lagging jacket to the cylinder, set the thermostat to around 60 degrees, and use a timer so the water is hot when you need it rather than all day. Turning the heater on only for the boost you actually need makes the biggest difference.
Questions
How much does an immersion heater cost to run?
A 3 kW element running for 2 hours uses 6.00 kWh, which costs £1.58 at 26.32p per kWh. A well-insulated cylinder then needs only brief top-ups to stay hot.
Is an immersion heater cheaper on Economy 7?
If you are on Economy 7 or a similar time-of-use tariff, heating the tank during the cheaper overnight period lowers the unit rate. On a standard single-rate tariff, as used here, the rate is the same all day.
Other appliances
Electricity rate: Ofgem energy price cap, 1 October to 31 December 2026, Great Britain average, Direct Debit, default tariff: 26.32p per kWh. Your own tariff and region may differ, so change the rate above to match your bill. Appliance figures are typical estimates; your appliance's energy label or manual is more accurate. Last checked 2026-11-03. Next review: January 2027, when Ofgem announces the next quarter's cap.