Electricity Cost Calculator
Calculate the estimated cost of running any household appliance based on its wattage and your local energy rates.
Runs in your browser Your input never leaves your device.
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About this tool
Enter an appliance's power in watts, how many hours a day it runs, the number of days and the price you pay per kilowatt-hour. The tool converts watts to kilowatts, then multiplies by hours and days to get energy in kWh: watts / 1000 x hours x days. The cost is that energy times your rate. Days start at 30, so by default you get roughly a month. Cost has no currency symbol, so it is shown in whatever currency your rate uses. The result is an estimate that assumes the device draws its rated power the whole time, which many devices do not. Everything is calculated in your browser.
How to use it
- Enter the device power in watts, from its label.
- Enter how many hours per day it runs.
- Set the number of days (30 by default).
- Enter your cost per kWh and read the energy and cost.
Example
0.150 kW x 8 h x 30 days = 36 kWh; 36 x 0.15 = 5.40.
150 W, 8 hours per day, 30 days, rate 0.15
Energy used: 36 kWh Cost: 5.40
How to calculate electricity cost by hand
Divide the power in watts by 1,000 to get kilowatts, multiply by the hours it runs to get kilowatt-hours, then multiply by your price per kWh.
kWh = watts / 1000 x hours per day x days cost = kWh x price per kWh 2000 W heater, 3 h a day, 30 days: 2 kW x 3 x 30 = 180 kWh 180 kWh x 0.30 = 54.00
Where to find each number
- Watts
- Printed on the appliance label, power adapter or manual. If the label only gives volts and amps, multiply them for an approximate figure: 230 V x 2 A is about 460 W.
- Hours per day
- How long the device actually runs. For things that cycle on and off, such as fridges and heaters with thermostats, use the time the motor or element is on, not the time it is plugged in.
- Price per kWh
- Shown on your bill as the unit rate. If you only have totals, divide the energy charge by the kWh used. Fixed daily charges and taxes are not part of the unit rate.
Watts, kilowatts and kWh
Watts measure how fast a device uses energy. A kilowatt-hour is the energy used by 1,000 watts running for one hour, and it is the unit your supplier bills you in.
A 100 W device takes 10 hours to use 1 kWh. A 2,000 W kettle uses the same 1 kWh in 30 minutes, which is why short bursts of high power can cost as much as long periods of low power.
Common problems
- The estimate is higher than my bill
- Rated watts are often a maximum. Fridges, heaters and many electronics cycle on and off, so average draw can be much lower.
- No result is shown
- Power must be greater than zero.
- I entered the rate in cents
- Use the same unit throughout. If your rate is 15 cents per kWh, enter 0.15 to get dollars, or 15 to get cents.
Frequently asked questions
How much does it cost to run a 1,000 watt appliance for an hour?
It uses 1 kWh, so the cost is exactly your price per kWh. At 0.25 per kWh it costs 0.25 an hour.
Does the result include standing charges or taxes?
No. The cost is energy times your rate only. Add fixed daily charges, taxes or tiered and time-of-use pricing from your bill separately.
How do I get a yearly cost?
Set Days to 365. For a device used only on some days, enter the number of days it is actually used.