The short answer
A heater drawing 1,500 W continuously uses 1.5 kWh per hour. Multiply 1.5 by your electricity price per kWh for the hourly cost, then by the hours actually used. Thermostat cycling can reduce consumption, so a full-power calculation is a scenario rather than a measured daily bill.
At full input, multiply your rate by 1.5
A heater drawing 1,500 W uses 1.5 kWh in one continuous hour. Its hourly electricity cost is 1.5 × your price per kWh. At an illustrative £0.28 per kWh, that is £0.42 per hour.
The electric-heater calculator gives an hourly figure at the entered power and extends your entered daily routine across the use days you choose.
Compare illustrative tariffs
These rates demonstrate the arithmetic. They are not current national tariffs, and the currencies are separate examples rather than exchange-rate conversions.
| Entered electricity price | One hour at 1,500 W | Five hours at 1,500 W |
|---|---|---|
| £0.28/kWh | £0.42 | £2.10 |
| $0.20/kWh | $0.30 | $1.50 |
| €0.30/kWh | €0.45 | €2.25 |
Use the rate charged for the relevant heating hours. If a bill states cents or pence, convert those units before entering a price in dollars, euros or pounds.
A thermostat changes the average
Five hours with a heater enabled need not mean five hours of uninterrupted full-power input. A thermostat can switch or reduce power after the selected temperature is reached; Pro Breeze explains this control behavior in its heater guidance.
The power-and-time estimate holds the entered draw constant. It does not assume that every heater runs for half the time, or that an oil-filled model has a particular duty cycle. A lower heat setting also needs its own appropriate input figure.
For a schedule that includes thermostat cycling, use a representative complete-day kWh sample. Suppose an illustrative three-day heater-only sample totals 12 kWh. Its daily average is 4 kWh, costing £1.12 per day at £0.28/kWh. That differs from the five-hour full-input example because it describes a different energy basis.
Count heating days for your season
At full 1.5 kW input for five hours on each of 30 use days, the estimate is:
1.5 × 5 × 30 = 225 kWh; 225 × £0.28 = £63.00.
For 90 otherwise comparable use days, it is 675 kWh and £189.00. Enter the period you intend to model. A seasonal heater should not automatically be assigned 365 days of use.
Keep the decision wider than the hourly price
Energy Saving Trust distinguishes direct or secondary electric heaters from heat pumps and whole-home heating arrangements. This calculator prices the selected appliance input; it cannot determine the heat your room needs or compare whole-house systems from heater watts alone.
Read oil-filled radiator versus fan heater costs to compare equal input with an equal heating task. Keep the thermostat setting, room conditions and schedule in your notes when repeating a measurement.