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Electricity Cost Calculator (kWh)

Enter the watts, the hours of use and your price per kWh to see what an appliance costs to run, or enter a bill to find your price per kWh.

This electricity cost calculator works out what electricity costs by multiplying the energy used, in kilowatt-hours (kWh), by your price per kWh. Use it as a kWh cost calculator for one appliance, or as a cost per kWh calculator that reads your rate from a bill.

Enter a device’s power, how long it runs and your price, and the tool shows the cost per day, per hour, per month and per year. It can also work backwards from a bill total and the kWh used to find your price per kWh. It runs in your browser, nothing is uploaded, and it is free with no sign-up. Results are estimates for planning.

Electricity cost calculator kwh example

How to use the Electricity Cost Calculator

  1. Open the “I want to” drop-down and choose “Find what an appliance costs to run” or “Find my price per kWh from a bill”.
  2. For an appliance, enter the Power and pick W or kW. The wattage is on the device label or data sheet.
  3. Enter the Number of units, such as 2 for two identical fans.
  4. Enter the Hours of use per day.
  5. Enter the Days of use per year. Use 365 for something used every day, and fewer for seasonal use such as a heater.
  6. Enter the Price per kWh (your currency) from your own bill. The pre-filled 0.1831 is only an example.
  7. For bill mode, enter the Bill total, the optional Fixed charges on the bill, and the kWh used on the bill.
  8. Read the result rows. Only the rows that match your chosen mode appear. Open “How it was calculated” to see each step with your numbers.

To try the tool quickly, press one of the example buttons above the form: Fan 200 W, Heater 1.5 kW, Computer 300 W, or Bill 120 for 800 kWh. Copy result gives the result lines with a link. Copy link stores every input in the page address, so the same calculation reopens later. Print / save as PDF opens a printable copy with the inputs, results, steps and date. Reset restores the starting example.

How do you calculate electricity cost?

Electricity cost is the energy used, measured in kilowatt-hours (kWh), multiplied by the price you pay per kWh. One kWh is 1,000 watts running for one hour, so a 1,000 W device running for one hour uses 1 kWh.

Work through it in three steps. First, find the daily energy: watts × hours per day × number of units ÷ 1000. (If power is already in kW, skip the ÷ 1000.) Second, find the yearly energy: kWh per day × days of use per year. Third, multiply by your price per kWh. The yearly cost is therefore kWh per day × days per year × price per kWh. The cost per month is the yearly cost ÷ 12.

Take a 200 W fan run for 4 hours a day, all year. 200 × 4 × 1 ÷ 1000 = 0.8 kWh per day. Over 365 days that is 292 kWh. At 0.1831 per kWh, the cost is 53.47 a year, or about 4.46 a month.

The same steps make this an electricity usage calculator and an electrical energy consumption calculator: before it multiplies by the price, it shows the energy used per day and per year in kWh, so you can read the consumption without a price by leaving the default price in place.

How do you calculate the cost per kWh from a bill?

Your price per kWh from a bill is the energy charge: the bill total minus any fixed charges, divided by the kWh used. Fixed charges are standing, connection or service charges that do not depend on how much you use, so they are taken off before the rate is worked out.

The formula is energy charge per kWh = (bill − fixed charges) ÷ kWh. The all-in price, which includes fixed charges, is bill ÷ kWh. Take a bill of 150 with 12 in fixed charges and 690 kWh used. The energy charge is (150 − 12) ÷ 690 = 0.2 per kWh. The all-in price is 150 ÷ 690 = 0.2174 per kWh.

Worked examples

InputResult
200 W, 4 h a day, 0.1831 per kWh0.1465 per day, 53.47 per year
1.5 kW, 2 h a day, 0.2 per kWh0.6 per day, 219 per year
100 W, 24 h a day, 0.1831 per kWh0.4394 per day, 160.4 per year
bill 150 with 12 fixed charges, 690 kWh0.2 per kWh

Calculated by the tool above with these values.

Frequently asked questions

How much does it cost to run a 100 watt device all day?

A 100 W device running 24 hours uses 2.4 kWh per day. Over 365 days that is 876 kWh, which costs 160.4 a year at 0.1831 per kWh, or about 0.4394 per day. Replace 0.1831 with the rate on your own bill for an accurate figure.

Where do I find the power of an appliance?

Look for the wattage on the device label or in the data sheet. Kilowatts (kW) work as well as watts. If the label only shows volts and amps, multiplying them gives an estimate of the watts (for AC loads the real power is lower by the power factor).

Why did the calculator warn that my price is above 1 per kWh?

A price above 1 per kWh is unusual, so the tool flags it. Check that the figure is per kWh and not per 100 kWh, and that it is not in cents. A rate of 18.31 cents, for example, should be entered as 0.1831 in a currency such as dollars.

Can this calculator work out the cost of charging an electric vehicle?

No. Electric vehicle charging is not covered here. This page is for appliances and household use.

How accurate are the results?

The results are estimates based on the numbers you enter. The calculation assumes the appliance draws its stated power for all the hours you enter; many appliances, such as refrigerators, cycle on and off, so measure with a plug-in meter if you need a closer figure.

Can I use the results in a quote, proposal or report?

Yes. Results, charts and printouts can be used freely in commercial work such as quotes, proposals, reports and service records. No attribution is needed.

Sources