Enter Values
Formula
Energy (kWh) = watts ÷ 1000 × hours/day × days
Cost = energy × rate per kWh
Example
A 1,500 W load used 4 hours per day for 30 days uses 180 kWh. At $0.16/kWh, it costs $28.80.
Choosing the Right Wattage
Use measured input power when possible. A device's maximum nameplate wattage may be higher than its normal consumption, while thermostatically controlled or variable loads may cycle throughout the day.
For cycling equipment, use average watts or multiply running watts by the fraction of time the device actually runs.
Understanding Utility Rates
Enter the energy charge in dollars per kWh. A utility bill may also include fixed customer charges, taxes, time-of-use rates, demand charges, fuel adjustments, and tiered pricing that this simple estimate does not include.
For a complete bill estimate, review the tariff and use the marginal rate that applies to the additional energy.