Electric Heater Running Cost Calculator

Portable resistive heaters are straightforward to estimate when they are drawing their full rated power. Thermostats can reduce average consumption once a room reaches temperature.

Appliance power (watts)Hours per sessionSessions per weekElectricity rate (pence/kWh)

Energy per session8.000 kWh

Cost per session£2.11

Weekly£14.74

Monthly estimate£63.87

Annual estimate£766.44

Formula: watts ÷ 1,000 × hours × electricity rate. This is an estimate; cycling appliances may draw less than their full rated power for part of the session.

What the result means

A thermostat may cycle the heater on and off, reducing real energy use below the maximum estimate.
This calculator does not compare whole-home heating systems or recommend electrical work.
Never exceed the manufacturer's installation and safety instructions.

Related guides

Read more about the topics covered by this calculator:

How this calculator works

Formula

Watts ÷ 1,000 × hours × electricity rate (pence/kWh) = cost in pence

Inputs

Heater power in watts
Hours per session
Sessions per week
Electricity unit rate in pence per kWh

Outputs

Energy per session (kWh)
Cost per session
Weekly cost
Monthly estimate
Annual estimate

Assumptions

Resistive heaters draw close to their rated power when the heating element is on.
Thermostats reduce average consumption once the room reaches temperature.
This estimate represents maximum cost; real cost may be lower with a thermostat.

Example calculation

A 2,000W heater running 4 hours at 26.32p/kWh: 2,000 ÷ 1,000 × 4 × 26.32 = £2.11 per session.

Tariff source

Default rates from Ofgem. Override in calculator.

Limitations

Thermostatic control reduces average power draw below rated wattage.
Fan heaters heat faster but use similar energy to oil-filled radiators over time.
Never exceed manufacturer safety instructions for portable heaters.