Electricity Cost Calculator
Enter the power of an appliance, the hours it runs and your price per kWh. The calculator shows how much energy it uses and what it costs per day, month and year.
How to use this Electricity Cost Calculator
- Find the power in watts on the label of the appliance. If it is given in amps, use the Watts to Amps Calculator.
- Enter the hours the appliance runs on a typical day.
- Enter how many days a month you use it.
- Enter the price per kWh from your latest bill.
- Add the number of identical appliances, then press Calculate.
How to calculate electricity cost
Energy is power times time. Cost is energy times price.
- kWh per day = watts x hours / 1,000 x number of appliances
- kWh per month = kWh per day x days of use
- Cost = kWh x price per kWh
- Cost per year = monthly cost x 12
Worked example
A 1,500 W space heater runs 3 hours a day for 30 days. It uses 1,500 x 3 / 1,000 = 4.50 kWh a day, which costs $0.72 at $0.16 per kWh. That is 135.0 kWh and $21.60 a month, or 1,620 kWh and $259.20 a year.
A heater with a thermostat does not draw full power all the time, so the real figure is often lower. The label shows the maximum power, and the average depends on how often the thermostat cycles. For items such as a fridge, which cycle on and off, use the daily energy from a plug-in meter if you have one. Run the calculator for a few appliances to find which ones cost the most, then look at ways to reduce their use. Small savings add up across a home. Switching to efficient lighting, using a power strip to cut standby loads, and running big appliances at off-peak times if your plan has time-of-use rates can all lower the bill. Compare the yearly cost with the price of a newer, more efficient model to see if replacing an old appliance would pay for itself.
Assumptions & limits
- The calculator assumes the appliance draws its labelled power the whole time it runs. Many appliances cycle or use less.
- The price per kWh is one flat figure. Real bills include fixed charges, tiers and time-of-use rates.
- Standby power is not included unless you enter it as hours of use.
- Taxes and fees on your bill are not included.
- A year is taken as 12 months of the same use.
Frequently asked questions
How do I calculate the cost of running an appliance?
Multiply the watts by the hours, divide by 1,000 to get kWh, and multiply by your price per kWh.
What is a kWh?
A kilowatt-hour is the energy of 1,000 watts used for one hour.
Where do I find my price per kWh?
On your electricity bill. Divide the energy charge by the kWh used, or look for the rate line.
Does standby power cost money?
Yes. Many devices draw a small amount all the time, which adds up over a year.
Why is my real cost different?
Appliances cycle, bills have fixed fees, and some rates change by time of day.
How can I measure real use?
A plug-in energy meter shows the actual kWh an appliance uses.
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Last updated: November 2026