Calculator
kWh to cost calculator
Already know your kWh? Turn it straight into dollars, and back again.
How to use it
Set watts to 1,000 and hours to your kWh figure — the calculator treats 1,000 W × 1 hour as exactly 1 kWh, so a reading of 42 kWh becomes 42 hours at 1,000 W. Change the rate to your blended cost per kWh and read the monthly figure.
Working backwards from a bill
If your bill says 812 kWh and $134, your blended rate is 16.5¢. Enter that rate once and every appliance estimate on this site matches your actual bill instead of the national average.
Why kWh is the right unit
Watts describe the speed of energy use; watt-hours describe the total. Utilities bill in kWh because it normalises across devices — a 15 W router running a month and a 1,500 W heater running 7.2 hours are both around 10–11 kWh.
Frequently asked questions
What formula does this use?
Cost = watts ÷ 1,000 × hours × rate. Kilowatt-hours are watts divided by 1,000, multiplied by hours of use.
Where do I find my electricity rate?
Divide the total on your last bill by the kWh used. That blended figure includes distribution and fees, so it is more accurate than the advertised rate.
Is this free to use?
Yes. No sign-up, no limits, and nothing you type leaves your browser.