Estimate electricity usage in kWh
Enter the appliance wattage, hours used per day, days and the energy-only rate from your utility plan. Energy (kWh) = watts ÷ 1,000 × daily hours × days; estimated energy charge = kWh × rate. A watt measures power; a kilowatt-hour measures energy.
Realistic worked examples
A 1,500 W appliance used for two hours per day over 30 days consumes 90 kWh. At an illustrative $0.18/kWh the energy charge is $16.20. A 10 W LED lamp used five hours daily for 30 days consumes 1.5 kWh, or $0.27 at that same illustrative rate.
Why the actual utility bill can differ
The calculation assumes constant wattage and one electricity rate. Variable appliance draw, standby consumption, taxes, fixed charges and time-of-use rates are not included. Read the US Department of Energy energy-use guide for methods to estimate appliance consumption. Compare scenario differences with the percentage calculator.
Additional formula and FAQs
Formula: kWh = watts / 1000 × hours per day × number of days; estimated energy charge equals kWh multiplied by the rate you enter.
Example: a 1,500 W appliance used 2 hours daily for 30 days consumes 90 kWh. At an illustrative $0.18/kWh this is $16.20 in estimated energy charges. Actual bills can also contain fixed fees, taxes, tiered rates, peak rates and variable appliance draw.
Frequently asked questions
Does it use a national electricity rate?
No. US rates vary; you must enter your actual price per kWh.
Does the calculator include demand charges and fixed fees?
No. It estimates energy charges only.