Last reviewed: 1 August 2026 by the Ozbuyz Store Editorial Team.
Quick answer: Multiply the heater’s rated input in kilowatts by the hours used and your electricity tariff in dollars per kilowatt-hour. This gives a full-power estimate. Actual consumption may be lower when a thermostat cycles the element, but it can approach the maximum in a cold or draughty room.
The running-cost formula
Cost = input power (kW) × operating time (hours) × tariff ($/kWh).
Convert watts to kilowatts by dividing by 1,000. For example, 2,000 W equals 2 kW. Use the usage rate from your own electricity bill rather than an online average because tariffs vary by retailer, plan, location and time of use.
Hypothetical full-power examples
The table uses an example tariff of $0.30 per kWh only to demonstrate the calculation.
| Rated input | Energy used in one full-power hour | Example cost per hour at $0.30/kWh | Example cost for 5 hours |
|---|---|---|---|
| 1.0 kW | 1.0 kWh | $0.30 | $1.50 |
| 1.5 kW | 1.5 kWh | $0.45 | $2.25 |
| 2.0 kW | 2.0 kWh | $0.60 | $3.00 |
| 2.4 kW | 2.4 kWh | $0.72 | $3.60 |
At a different tariff, replace $0.30 with the rate on your bill. Do not treat the examples as a forecast of your seasonal bill.
Why actual use differs from the maximum
A resistance heater draws its rated input while the element is operating. A thermostat may switch the element off and on after the room reaches the setting. The proportion of time it remains active depends on outdoor temperature, set point, insulation, glazing, draughts, room volume, door position and heater placement.
Features labelled “eco” do not create free heat. They may lower the power setting, change the thermostat target or manage cycling. Check the manual to understand what the mode actually does.
Does heater type change the cost?
At the same rated input and full-power run time, panel, oil-column, fan and radiant resistance heaters use the same amount of electricity. Type affects how quickly and where the heat is felt, which can affect the time you choose to run it. That behavioural difference is important, but it is not a special efficiency advantage at the element.
Compare with reverse-cycle heating
Reverse-cycle air conditioners move heat rather than generating it solely through electrical resistance. Australian Government guidance says they can deliver several units of heat per unit of electricity and are generally more efficient for space heating. Compare correctly sized systems using the Zoned Energy Rating Label and your climate zone.
Build a realistic weekly estimate
- Write down the heater’s rated input in kW.
- Use your current tariff from the bill.
- Estimate weekday and weekend hours separately.
- Calculate a worst-case full-power figure.
- Track actual use for a week and compare it with the next bill or a suitable energy monitor.
- Repeat after changing thermostat settings or draught control.
Ways to reduce cost without unsafe shortcuts
- Heat the occupied closed room rather than an unnecessary larger zone.
- Use the thermostat at a comfortable, not excessive, setting.
- Seal avoidable draughts without blocking required ventilation.
- Close suitable curtains or blinds as the room cools.
- Use clothing and bedding appropriate to the season.
- Switch the heater off when the room is unoccupied.
- Compare your electricity plan using current official or regulated comparison resources available in your state.
Frequently asked questions
How much does a 2,000 W heater cost per hour?
At full power it uses 2 kWh per hour. Multiply 2 by your tariff. At $0.30/kWh the example is $0.60 per hour; at $0.40/kWh it is $0.80.
Does a thermostat reduce electricity use?
It can reduce active heating time once the room reaches the set point. The saving depends on the setting and how quickly the room loses heat.
Is an oil-column heater cheaper to run?
Not merely because it contains oil. A resistance heater’s maximum electricity use is determined by its rated input. Oil columns differ in heat delivery and thermal response, not in a special per-watt conversion advantage.
Why is my bill higher than the simple calculation?
The bill includes other appliances, supply charges and possibly different time-of-use rates. Confirm the tariff, actual hours, heater setting and whether other loads increased during the same period.
Research and review method
The calculation follows the standard kWh method used in Australian Government Energy Rating information. Efficiency comparisons are based on current government heating-and-cooling guidance.