30 · Calculators

Electricity Cost Calculator

Enter a device’s power, how long you use it each day and your electricity price to see what it costs to run.

On the label or charger. 1 kW = 1,000 W.

Cost per month

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How to use the electricity cost calculator

  1. Enter the power in watts from the label or charger.
  2. Enter how many hours a day it’s on.
  3. Enter your price per kWh from your bill.

How it works

Energy in kWh is watts × hours ÷ 1,000. A 150 W device used for 5 hours uses 0.75 kWh a day. Multiply by your price per kWh to get the cost. Monthly cost uses an average month of 365 ÷ 12 days.

Getting an accurate figure

  • The label shows maximum power; many devices use less most of the time.
  • Fridges and heaters cycle on and off, so estimate the hours they actually run.
  • A plug-in energy meter gives the most accurate numbers.

Examples

150 W for 5 hours a day at 0.17 per kWh

3.88 a month · 46.54 a year

2,000 W heater, 3 hours a day at 0.30 per kWh

54.75 a month

Questions

Where do I find the wattage?

On the appliance’s label, its power adapter or its manual. If it lists amps, multiply by your voltage to get watts.

What’s a typical electricity price?

It varies widely by country and supplier. Your bill shows your price per kWh.

Can I add several devices?

Use the number of devices field for identical ones, or add up separate results.