The core formula
Divide watts by 1,000 to get kilowatts. Multiply by operating hours to get kWh, then multiply by your all-in variable electricity price.
Use realistic runtime
A refrigerator, air conditioner or sump pump cycles. The label wattage multiplied by 24 hours usually overstates consumption. A plug-in meter or smart-device history can provide average draw.
Separate fixed charges
A fixed monthly customer charge does not increase when one appliance runs longer. Leave it out of marginal appliance decisions, but include it when estimating the entire bill.
Editorial standard
This guide explains general billing math. Utility tariffs and local rules control your actual charges. Sources and update practices are documented in our methodology.
Read the methodology →