The formula
Running cost comes down to two steps. First, energy:
kWh = watts ÷ 1,000 × hours. Then cost:
kWh × your rate ($/kWh). A 1,500 W heater for 8 hours uses 12 kWh;
at $0.19/kWh that is about $2.28 a day. The calculator runs that math across
every period so you can see the hourly, monthly, and yearly picture at once.
Use your own numbers
The presets are indicative typical wattages — handy for a ballpark, but
your model may differ. For the most accurate result, enter the watts from the appliance's
label and the $/kWh from your electricity bill. Cycling appliances like
fridges and AC don't run flat-out all day, so they use an effective-average wattage or
equivalent run-hours.
Indicative typical wattages and a ~$0.19/kWh US average rate, as
published for 2026-04. Appliance presets reviewed 2026-06. Use your bill for
accuracy.