Short answer: Convert watts to kilowatts, multiply by hours, then multiply by the electricity rate. Treat the result as an estimate because thermostats, compressors, standby modes, and user behavior change real consumption. We would diagnose the number before trying to lower it. Separating usage, billing days, rates, and fixed charges prevents an expensive answer to the wrong problem.
Use the simple equation
Estimated cost equals watts divided by 1,000, multiplied by hours used, multiplied by the price per kilowatt-hour. Use the rate that actually applies to the bill, including time-of-use rules when relevant.
Know when the equation overstates reality
A refrigerator, air conditioner, heat pump, water heater, and dehumidifier cycle rather than drawing full rated power continuously. Nameplate watts are a starting point, not a promise of daily use.
Measure the important loads
A plug-in meter can help with compatible small appliances. Whole-home loads, hard-wired equipment, and high-current devices need appropriate measurement by qualified people or utility data.
Use this checklist
- Record the device wattage or measured draw and the daily hours.
- Convert watts to kilowatts before multiplying by hours and rate.
- Adjust for cycling, standby, seasonal use, and different operating modes.
- Compare the estimate with the bill or a meter reading before making a purchase decision.
When to stop
- Do not plug a meter or extension cord into equipment it is not rated to handle.
- Do not open hard-wired appliances or service panels for measurement.
- Use local rates, taxes, and program rules rather than assuming a national average.
Sources
These official references were used for the factual guidance and limits above.