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Electricity Cost Calculator

Enter a device's wattage, daily usage, and your electricity price to see what it really costs.

Result

How it is calculated

The tool converts power to energy and then to money. Daily energy in kilowatt-hours is kWh/day = (watts ÷ 1000) × hours per day. Daily cost is kWh/day × price per kWh. Monthly cost multiplies the daily cost by 30 and the yearly cost multiplies it by 365. Enter the device's power in watts, the hours it runs per day, and the tariff per kWh in the currency you want back. The method assumes constant power draw every day; real appliances cycle (fridges, heaters with thermostats) so average consumption is often lower than the label. Tariff changes, tiered rates and taxes are not modelled.

Worked example

A 150 W device runs 8 hours a day at a price of 0.15 per kWh. Energy: 150 / 1000 × 8 = 1.20 kWh per day. Daily cost: 1.20 × 0.15 = $0.18. Monthly (30 days): 0.18 × 30 = $5.40. Yearly (365 days): 0.18 × 365 = $65.70. That gives you a figure to compare against a more efficient model.

Try this example →

Common mistakes

  • Entering the wattage as kW (or the reverse), which changes the cost by a factor of 1,000.
  • Using the price of a full bill that includes fixed fees instead of the price per kWh.
  • Using the nameplate power for a cycling appliance; its average draw can be much lower.
  • Forgetting standby consumption of devices that stay plugged in all day.

About this calculator

This calculator multiplies a device's power draw in watts by how many hours a day you run it and your local electricity price per kilowatt-hour, converting raw wattage into an actual money figure — the daily, monthly and yearly cost of keeping that appliance running.

It's used by anyone trying to find where their electricity bill is going: households comparing the running cost of an air conditioner versus a space heater, renters deciding whether an old refrigerator or water heater is worth replacing, and small business owners estimating the cost of equipment like servers or freezers that run continuously. Because electricity prices and tariffs vary a lot by country and utility, plugging in your own rate turns a generic wattage spec on a device's label into a cost that's specific to your bill.

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Comments (1)

  • Editorial team

    The wattage on a nameplate is the maximum draw. A fridge or a heater cycles on and off, so a plug-in energy meter reading gives a truer average than the label. Devices left on standby use a little power for all 24 hours, which adds up over a year. The monthly line is 30 days and the yearly line is 365 days, so yearly is not simply twelve times monthly. Which appliance are you testing?

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