Calculate the cost of an electric heater
For an electric resistance heater, multiply electrical power in kW by hours of operation to get kWh. Multiply those kWh by your electricity price to get the cost. Divide watts by 1,000 before entering them: a 2,000 W heater is 2 kW.
At an example tariff of 0.30/kWh, a 2 kW heater operating continuously costs 0.60 per hour. Five hours costs 3.00. Using it for five hours on 180 days costs 540. The default example uses these values and assumes full power throughout the entered hours.
What if the thermostat switches it off?
“Average power use” allows for a heater that cycles on and off. If it draws full rated power for approximately half of the scheduled time and negligible power for the remainder, enter 50%. In the example above, that halves the estimated energy cost to 270.
This percentage is your assumption, not something the calculator can infer from room size. Insulation, outside temperature, draughts and thermostat settings all affect actual consumption. An energy meter can help establish average use where it is suitable for the appliance.
Oil-filled radiator, fan heater or heat pump?
This calculation models direct electric resistance heating at one kWh of heat per kWh of electricity. Different controls and heat distribution can change comfort and the hours needed, but the model does not assign an invented energy multiplier to an oil-filled radiator or fan heater.
A heat pump is a different system. It moves heat and can deliver several kWh of heat per kWh of electrical input. Add “Heat pump / AC” to compare the cost of delivering the same quantity of useful heat. Installation cost and suitability for your room remain separate questions.
Interpret the annual and monthly totals
The annual estimate covers exactly the number of heating days you entered. The monthly average divides that total by twelve, including months when you might not use the heater. For a single day, enter one day; the result then represents that one-day usage scenario.
See the formulas and assumptions, or compare heating with an air conditioner.