The Utility Energy Calculator estimates electricity use, monthly energy cost, and annual cost from appliance power, daily operating time, electricity price, and the number of similar devices. It is useful for checking how much a space heater, air conditioner, computer, or other appliance may add to a bill.
The results distinguish energy consumption from cost, helping you compare appliances with different wattages or estimate savings from shorter run times. Because actual consumption can cycle or vary by operating mode, the estimate works best as a planning range rather than a bill prediction.
Enter your values
W
hours
days
$/kWh
devices
%
Result
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Estimated monthly electricity cost
Monthly energy use—
Daily energy use—
Estimated annual cost—
Annual energy use—
1. Enter the wattage Use the rated power shown on the appliance label or specification sheet.
2. Set daily operating time Enter the average number of hours the appliance runs each day.
3. Choose active days Enter how many days per month the device is used.
4. Add the electricity rate Use the energy charge per kilowatt-hour from your utility bill.
5. Enter device count Use the number of identical appliances operating on the same schedule.
6. Adjust the duty cycle Reduce the percentage when the device cycles off or draws full power only part of the time.
Daily kWh = (Watts ÷ 1,000) × Hours per day × Devices × Duty cycle Monthly kWh = Daily kWh × Days used Monthly cost = Monthly kWh × Rate per kWh
The duty cycle is entered as a percentage and converted to a decimal. The calculation assumes the entered wattage represents active power draw.
What the result means
The main result is the estimated monthly electricity charge attributable to the entered device use.
Utility bills may also include fixed charges, demand charges, taxes, and tiered rates.
Given: 1,500 W heater, 4 hours per day, 30 days, $0.17/kWh, one device, 100% duty cycle.
Result: $30.60 per month and about $367.20 per year.
Interpretation: Running the heater on this schedule adds roughly 180 kWh to monthly consumption.
Where can I find appliance wattage?
Check the product label, manual, power adapter, or manufacturer specifications. A plug-in power meter can provide a more realistic measured value.
What duty cycle should I use?
Use 100% for devices that draw near-rated power continuously. For thermostatically controlled equipment, estimate the percentage of time the compressor or heating element is active.
Does the calculator include standby power?
Only if standby wattage and hours are entered as a separate calculation. Standby consumption is often much lower than active use.
Why does my bill not match the estimate?
Bills include all devices, fixed utility charges, rate tiers, and changing usage. Appliance power may also differ from the nameplate rating.
Can this compare two appliances?
Run the calculator once for each appliance using the same schedule and rate, then compare monthly kWh and cost.