Energy Cost Calculator
Work out the running cost of an appliance or device from its wattage, usage hours and electricity rate, free in your browser.
Enter Values
Minimum 0
Range 0–24
Minimum 0
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the appliance power in watts, hours used per day and your electricity price.
- Press Calculate for the running cost.
How it works
Daily energy = power (W) ÷ 1000 × hours used. Multiply by the price per kWh for the daily cost, then scale up to a month and a year.
Worked example
100 W for 24 h at $0.30/kWh. 2.4 kWh/day × $0.30 = $0.72 a day.
Common mistakes
- Mixing watts and kilowatts — divide watts by 1000 before multiplying by hours and tariff.
- Using the peak tariff for everything — many bills have separate peak, off-peak and supply charges.
Frequently asked questions
How is the running cost calculated?
Cost = power in kW × hours used × your rate per kWh. A 2,000 W heater for 3 hours at 30c/kWh is 2 × 3 × 0.30 = $1.80.
Why is my real bill higher?
Bills add a daily supply charge, GST and sometimes tiered or time-of-use rates, so per-appliance running cost is only part of the total.
Why doesn't this match my bill?
Bills also include daily supply charges, tiered tariffs and GST.
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Cite this tool
Zerdly. (2026). Energy Cost Calculator. Retrieved from https://www.zerdly.com/tools/energy-cost-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.