Household energy
Estimate what an appliance costs to run.
Convert watts and usage time into kilowatt-hours, then apply the rate from your electric bill.
Estimated cost
Enter the appliance and rate details.
Estimated cost
Per average month
Daily
Monthly
Yearly
Energy formula
Cost = kilowatt-hours x dollars per kilowatt-hour.
Use the actual power draw when possible
A nameplate may show maximum power rather than typical use. Refrigerators, air conditioners, heaters, and computers can cycle or change power levels, so a plug-in energy meter or a measured kWh figure usually produces a better estimate.
Watts measure power
Watts describe the rate at which a device uses energy at a moment in time. One kilowatt equals 1,000 watts.
Kilowatt-hours measure energy
A 1,000-watt device running for one hour uses 1 kWh. A 100-watt device running for ten hours uses the same amount.
Bills can be more complex
Utilities may use seasonal rates, time-of-use periods, tiers, demand charges, taxes, and fixed service fees. This tool applies one flat energy rate.
The U.S. Energy Information Administration explains that watts measure power while watt-hours measure energy used over time.
Worked example: a 1,000-watt appliance used for 2 hours per day uses about 2 kWh per day. At a flat rate of $0.15 per kWh, that is about $0.30 per day or $9 for a 30-day month.
Assumptions: the entered wattage and usage schedule remain constant, and the rate is a flat energy charge. Real bills may include fixed fees, tiers, demand charges, taxes, or time-of-use pricing.
This calculator is an estimate. Confirm device power, duty cycle, and the applicable rate structure for budgeting or equipment decisions. Do not measure live electrical circuits unless you have the proper equipment and training. Method and source link reviewed September 29, 2026.
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