Appliance energy cost

Power is a rate. Your bill uses energy over time.

Daily kWh = appliance count × (active watts × active hours + standby watts × standby hours) / 1000. Active hours = window hours × duty percentage / 100. Standby hours = 24 − active hours. Period kWh = daily kWh × days; estimated energy charge = period kWh × your flat rate.

For example, 1500 W for 3 hours/day over 30 days uses 135 kWh with no standby. At 0.20 per kWh, the energy charge is 27.00 in your chosen currency. Add 10 W standby for the other 21 hours/day and the estimate becomes 141.3 kWh and 28.26.

Nameplate power can differ from actual use; cycling, operating modes and behavior matter. Enter your own measured or estimated inputs. Do not automatically apply a duty reduction to power that is already a measured average. This tool assumes the same daily pattern and a constant rate, so it is not a forecast of your complete electricity bill.

Numeric relationships use exact rational arithmetic. Cost rounds to your selected 0–6 decimal places, with exact halves rounded away from zero; this does not establish the precision of your measurements. Reference for W × hours / 1000 and kWh × rate: Virginia Cooperative Extension, Estimating Appliance and Home Electronic Energy Use, authored by Robert Grisso, Martha Walker and John Ignosh. This tool does not use that publication’s dated appliance-wattage examples.