How to measure appliance energy across a full operating cycle
A momentary watt reading shows what an appliance is doing now. For equipment that changes stages, accumulated kWh over a complete cycle is usually the better cost input.
Define the measurement boundary
For a washer, include the whole selected program. For refrigeration, choose an interval long enough to include cooling, idle periods and recurring defrost events. Record load, program, room conditions and elapsed time. Use a meter suitable for the appliance and outlet; hardwired or high-current equipment needs an appropriate monitoring method.
Convert accumulated energy to average power
Suppose a fictional freezer measurement records 2.4 kWh in 48 hours. Average power is 2.4 × 1,000 ÷ 48 = 50 W. Enter 50 W, 24 hours, 30 days and 100% duty cycle: the projection is 36 kWh. At an illustrative USD 0.22/kWh, that is USD 7.92. The 48-hour measurement includes idle time, so applying another duty factor would count it twice. Read the meter’s stated accuracy and display resolution before interpreting a small difference between two tests.
A longer cycle need not use more energy
A washer using 0.50 kWh per cycle over 16 similar cycles consumes 8 kWh. A two-hour program does not imply twice the energy of a one-hour program; pauses and heating stages matter. Represent this measurement as 500 W for one hour, with 16 one-cycle sessions in the Days field and 100% duty. This is an energy-equivalent entry, not its actual runtime.
A wall meter includes electricity passing through that outlet, including accessories. It does not measure hot water supplied by a separate heater. Do not add motor energy already captured by the meter. Keep measurements for different programs separate and retain unrounded kWh until the final price calculation.
Appliance Energy Cost Calculator
Worked example: Turn a washer cycle reading into a monthly cost
Related reading: Rated power is not average power
Reference: Virginia Tech Extension: estimating appliance energy use.