Energy Use & Cost
Energy Use & Cost calculators — each with the formula, a worked example and a reference table. Results are estimates for planning and education; verify all sizing with a licensed electrician and your AHJ.
Appliance Energy Cost
Find out what any appliance costs to run. Enter its power in watts, how many hours a day y…Electricity (kWh) Cost
A quick way to turn watts and hours into kilowatt-hours and a dollar cost. Enter the power…EV Charging Cost
Estimate what it costs to charge an electric car at home. Enter the battery size, the star…Energy is watts times hours — cost is energy times your rate
Every running-cost question on this site comes down to one idea: energy in kilowatt-hours is power in watts multiplied by the hours it runs, divided by 1,000, and the cost is that energy times the price you actually pay per kilowatt-hour. We deliberately hold no tariff list — you read the rate off your own utility bill and enter it — so the tools stay correct in any country or currency and need no maintenance. That single input is also where most surprises hide: a small always-on device costs far more over a year than a large appliance used briefly, because hours, not watts, dominate the bill.
Use the Appliance Energy Cost calculator to price any device from its wattage and how long it runs, over a day, a month or a year. The Electricity (kWh) Cost calculator works the other way, turning a measured or estimated energy figure straight into money. For electric vehicles, the EV Charging Cost calculator adds the charging efficiency loss so the number reflects the energy drawn from the wall, not just the energy stored in the battery.
To see the method applied end to end, read the cost to charge an EV at home. These are estimates based on the rate and usage you enter; your real bill also carries fixed charges, taxes and tiered or time-of-use pricing that a flat per-kWh figure cannot capture.