Guide 07 / 10
Why a refrigerator or air conditioner is hard to estimate from its label
Understand cycling and variable power before treating a simple watt-hour estimate as a bill prediction.
A cycle is not full-time draw
Refrigerator and air-conditioner compressors can start and stop automatically. Many modern units also vary their speed. Multiplying maximum watts by 24 hours is usually not a realistic account of their use. Ambient temperature, settings, room size, door opening, and maintenance all affect the outcome.
Choose suitable data
If an energy label states kWh over a period, use that figure while noting its official test conditions. To learn about your own home, a kWh measurement over a representative period is more useful than one momentary watt reading. Avoid comparing days with very different weather.
Describe uncertainty
Watts × hours can still illustrate a bound under a stated assumption, but it is not a guaranteed bill. Name the assumptions, record where the watt figure came from, and revise the estimate when you have measurements. Do not use a calculator result to diagnose equipment faults.