Calculate from miles instead of battery size
For a monthly budget, miles driven and vehicle efficiency are more useful than the battery's full capacity. Divide monthly miles by miles per kWh, adjust upward for charging losses, and multiply the wall energy by the electricity rate.
A simple example
A driver covering 1,000 miles at 3.5 miles per kWh needs about 286 kWh in the battery. At 90% charging efficiency, the wall supplies about 317 kWh; at an illustrative $0.18 per kWh, that is about $57 for the month.
Change each input to match the car, season, route, and utility plan rather than treating the example as a national price quote.
Time-of-use pricing can change the answer
Some utilities charge different prices by hour or offer a dedicated EV plan. Separate off-peak and on-peak kWh instead of applying one average rate when the charging schedule spans both periods.
- Use the energy rate from the bill, including applicable riders.
- Add a new fixed monthly charge only if changing to the EV plan creates it.
- Check the plan's exact off-peak start time before scheduling.
Why charger wattage is not the monthly bill
A 7.2 kW charger can deliver energy faster than a smaller unit, but it does not automatically use more energy for the same driving. Wattage determines charging speed; miles, vehicle efficiency, losses, and price determine the longer-term energy cost.
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