How to measure appliance electricity use
For a refrigerator, dehumidifier or other cycling device, a momentary watts reading can be misleading. Recording total kWh across a representative period captures the on-and-off pattern.
Choose the right measurement
Use a compatible plug-in energy meter only within its voltage, current and load ratings and the appliance instructions. This is a measurement workflow, not wiring guidance. Hardwired equipment needs suitable installed monitoring or qualified help; do not improvise a plug connection.
- Record appliance model, mode and settings. Note relevant conditions such as room humidity or temperature.
- Record the starting accumulated kWh and start time.
- Use the appliance normally across several representative days. Include idle time if it belongs to the use pattern you want to price.
- Record ending kWh and time. Subtract the starting reading.
- Divide measured kWh by elapsed hours, then multiply by 24 for an equivalent daily average.
Worked example: three days of observation
This is illustrative arithmetic, not a test of a particular appliance. Suppose the meter moves from 12.40 to 16.00 kWh over exactly 72 hours. Consumption is 3.60 kWh. That is 0.05 kWh per elapsed hour, equivalent to an average draw of 50 W, or 1.20 kWh/day. At $0.18/kWh, a 30-day projection costs $6.48.
The 50 W average does not mean the appliance draws exactly 50 W whenever it runs. A compressor can alternate between higher active power and lower idle power. To use our electricity calculator, enter the measured average of 50 W and 24 hours, or use a representative active power with its actual active hours. Do not count the duty cycle twice.
Make comparisons repeatable
- Record elapsed time precisely instead of calling every measurement “a day.”
- Keep settings comparable, or label the reason for changing them.
- Log doors opened, loads processed or operating conditions where relevant.
- Repeat in a different season before claiming year-round consumption.
- Keep the original readings; record a correction rather than silently replacing a result.
What a short test cannot establish
A few days cannot establish a universal model average, annual performance or savings caused by a change. Weather and behavior can move with the change you are evaluating. Report the measurement period and conditions alongside the result, and describe projections as projections.
From energy to cost
Multiply measured kWh by your variable price per kWh. If consumption spans different tariff windows, a total kWh counter alone cannot assign energy to each window; use interval records or separate readings. The time-of-use calculator keeps that split explicit.
Method and sources
WattWorth · Published September 17, 2026. AI-assisted educational content; examples are calculated illustrations, not product testing. Editorial approach.
Energy calculations use watts ÷ 1,000 × hours = kWh. U.S. Department of Energy: Electricity 101 · DOE energy education: kWh formula