A clearer electric bill starts with three numbers.

Power, time, and price. Together they explain the energy cost of an appliance.

1. Start with the power actually used

Watts describe the rate of energy use. A 1,000-watt device uses one kilowatt-hour when it runs at that power for one hour. A label often describes rated power; actual consumption may change with settings and cycling. A compatible energy meter can measure kWh over time.

2. Count operating hours

A lamp running five hours a day is straightforward. A refrigerator is less so: its compressor switches on and off. For cycling equipment, a measured daily kWh figure or manufacturer annual energy estimate is more useful than assuming its rated watts run all day.

3. Find your variable rate

Look for energy charges per kWh, including applicable variable delivery charges. Convert cents to dollars: 18 cents is $0.18. A fixed monthly service charge stays the same when you use one appliance less. Time-of-use customers should calculate peak and off-peak operation separately.

A worked example

A 100-watt device used five hours per day consumes 0.5 kWh daily. Over 30 days, that is 15 kWh. At an illustrative $0.18/kWh, it costs $2.70. Reducing use to three hours per day lowers the estimate to $1.62, a difference of $1.08.

Compare changes fairly

Keep runtime and electricity rate the same when comparing device power. Keep device power the same when comparing schedules. Avoid treating a projection as guaranteed savings: weather, settings and behavior can change the result.

Check your estimate

Compare predicted energy with measured use over a representative week. If they differ, revisit average power and operating hours before changing the rate. For annual projections, account for seasonal use instead of multiplying a winter day by 365.

Sources & editorial note

U.S. Department of Energy: Electricity 101 · DOE energy education: kWh formula

Published September 17, 2026. This guide explains energy arithmetic; it does not provide electrical installation advice or claim hands-on product testing.