Turn watts into a cost
kWh = watts ÷ 1,000 × operating hours per day × days
Cost = kWh × cents per kWh ÷ 100
Cost = kWh × cents per kWh ÷ 100
A worked example
An illustrative 1,500-watt pump running 8 hours a day uses 12 kWh per day. Across 30 days that is 360 kWh, or $57.60 at an illustrative 16¢ per kWh. This is an example calculation, not a typical pump specification.
Operating time is not always switched-on time
A refrigerator or air conditioner cycles and may change its power draw. Nameplate wattage multiplied by all the hours it is connected can overestimate consumption. Use measured average power, measured kWh, or operating hours appropriate to your equipment.
What does the annual figure mean?
The annual projection uses 365 days at the same daily operating pattern and rate. It is not your entered-period cost multiplied by 12. Seasonal appliances may run for only part of the year.