How Much Does a Immersion Heater Cost to Run?
Updated March 2026. Default rate effective 1 April 2026 (Ofgem Q2 2026). Figures are typical estimates rather than model-specific guarantees.
An immersion heater costs approximately 94p per session and around £342 per year to run based on 1.5 hours daily use. It is one of the most expensive ways to heat water.
Calculator24.5p/kWh
W
hrs
p/kWh
Per hour
73.5p
Per day
£1.10
Per week
£7.72
Per month
£33.56
Annual cost
£402.41
Typical annual electricity use: 1642.50 kWh
Based on typical immersion heater usage at current rates.
Annual estimate
£402.41
Annual electricity use
1642.50 kWh
Typical household bill context
About 61% of a typical home's annual variable electricity spend at the current default rate.
What Affects the Cost of Running a Immersion Heater?
Immersion heater costs depend on: Heating duration — depends on tank size and starting water temperature. Tank insulation — a poorly insulated tank loses heat faster. Thermostat setting — setting the thermostat to 60°C is recommended.
Helpful guides
Related appliances
Assumptions and methodology
- Electricity rate: 24.5p/kWh (Ofgem Q2 2026)
- Default wattage is based on a typical appliance in this category
- Usage assumptions are meant to be a sensible starting point, not a fixed rule
- Costs vary with tariff, model, settings, load size, and household habits
Tips to Reduce Immersion Heater Running Costs
Use a timer to heat water only when you need it — heating water overnight when you do not use it wastes energy. Ensure your hot water tank is well insulated with a jacket at least 80mm thick.
Frequently asked questions
Common questions about electricity costs and our calculators.