Convert one day into one month
Multiply daily kWh by the number of days in the billing period, then multiply by the price per kWh. A device averaging 2 kWh per day uses about 60 kWh in a 30-day month.
Use the actual billing period
Utility billing periods are not always exactly 30 days. Use the start and end dates shown on the bill when comparing a monitor estimate with billed usage, especially if the daily load is large.
- Use 28, 29, 30, or 31 days for a calendar month.
- Use 365 days for a simple annual estimate, or 366 in a leap year.
- Match the energy rate to the same period when prices changed midyear.
Separate steady and seasonal loads
A refrigerator may have a fairly stable daily baseline, while air conditioning, heating, dehumidification, and pool equipment change with the season. Estimate typical days for each season instead of extending one unusually hot or mild day across the full year.
Know what the monitor includes
A plug-in meter rated for the appliance records only the device connected through it, while a circuit or whole-home monitor may include several devices. Check the meter's voltage, current, and load rating, then confirm what it covers before assigning all recorded kWh to one appliance.
Rate source and limits
The default rate is the EIA U.S. residential average for April 2026, retrieved July 16, 2026. It is an average revenue per kilowatt-hour, not a quote for your utility plan. Fixed fees, taxes, tiers, and time-of-use prices can change the bill.
Open the EIA source