Guide 03 / 10
Turn operating hours into monthly kWh
Build an estimate you can check: watts, hours per day, days of use, then kWh.
Start with one device
For a fairly steady load, use watts × hours per day × days used ÷ 1,000. Multiply by quantity if several identical devices follow the same schedule. Record whether your hours are a daily schedule, a weekly average, or a guess; the output can only be as good as the inputs.
Do not force 30 days
A device used only on workdays may run around 20 days, while a refrigerator stays connected all month but its compressor does not run continuously. Enter days that fit your own pattern. For bill comparisons, use the actual number of days in the billing period.
Separate kWh from money
kWh estimate energy. To estimate the energy charge, multiply kWh by a rate you know. Taxes, fixed fees, subsidies, tiered rates, and local rules can make the bill differ. Our calculator does not replace your provider's itemized statement.