Heating-energy estimator
Estimate the electricity cost of running a heater (electric heater, immersion heater, etc.) from its power rating, daily usage and your electricity price.
Result
Daily cost
Weekly cost
How to use this calculator
- Check the heater's power rating in kW (on the appliance label or manual).
- Estimate how many hours per day it actually runs (not necessarily how many hours it's switched on, if it cycles on/off via a thermostat).
- Enter your electricity price per kWh.
- Read the daily and weekly cost.
Assumptions
- Assumes the heater runs at full rated power for the hours entered — thermostatically controlled heaters often cycle at a lower average power, so this may overestimate cost for those.
Technical details: what the fields mean
- Heater power
heaterPowerKw - The heater's power rating in kW — check the appliance label.
- Hours used per day
hoursPerDay - Hours actually heating per day. A thermostatically controlled heater cycles on/off, so this may be less than the hours it's switched on.
- Electricity price
pricePerKwh - Your electricity price per kWh.
Methodology
Daily cost = power (kW) × hours × price per kWh. Weekly cost = daily cost × 7.
Worked example
2kW heater, 4 hours/day, 28p/kWh
Inputs: heaterPowerKw=2, hoursPerDay=4, pricePerKwh=0.28
Result: £2.24/day, £15.68/week
Practical guidance
- For a thermostatically controlled heater, estimate the effective "on" time rather than the total hours it's switched on at the wall, for a more accurate figure.
- Compare running costs between heater types (fan heater vs. oil-filled radiator vs. panel heater) using their respective power ratings.
Common mistakes
- Using the hours the heater is switched on rather than the hours it's actually drawing full power, which overestimates cost for thermostatically controlled heaters.
FAQs
How much does it cost to run a 2kW heater for 4 hours?
At 28p/kWh, about £2.24 — or £15.68 for a week of that daily usage.