Method: how the costs are worked out, and their limits
What the figures on this site are, where they come from, how they are calculated, and what they leave out. They are averages built from two public data sets, and they are a good estimate for comparing states and cars, not a quote for your bill.
Where the figures come from
EIA's Electric Power Monthly lists the average price of electricity to ultimate customers by state, by sector, in cents per kilowatthour.
EPA fuel economy ratings give each electric car's energy use in kWh per 100 miles.
State prices are the residential figures for July 2026, downloaded on 2026-10-16. Car ratings are for the 2025 model year, downloaded on 2026-10-16. The pages were built from those downloads by a script, so no number is typed by hand, and a check re-downloads both and compares before anything is published.
How the cost is calculated
- Per 100 miles. The car's kWh per 100 miles times the state's price per kWh, in dollars.
- Per month and per year. The per-100-mile cost scaled to 1,000 miles a month, or to 12,000 miles a year (the starting value in the calculator, which you can change).
- State comparisons. A reference car that uses 30 kWh per 100 miles, close to the middle of the 12 cars here. The ranking of states does not depend on the car.
What the figures leave out
- A state average is not your utility's rate. Rates differ by utility, plan and season, and the July 2026 figure is one month.
- Time-of-use plans can make overnight charging much cheaper than the average; fixed monthly fees can make it dearer.
- Energy ratings are laboratory-based. Cold weather, speed, towing and short trips use more energy than the rating.
- Charging away from home, at public fast chargers, costs more per kWh and is not included.
- The cars shown are one trim each of popular 2025 models; other trims and years use different amounts.
Where to go next
Try the calculator, see the state ranking or the car list, or open Texas or 2025 Tesla Model 3 Long Range RWD as examples.