EV home charging and off-peak rates

An electric vehicle's energy use here comes from fueleconomy.gov. The file retrieved October 10, 2026, supplies kilowatt-hours per 100 miles for city, highway, and combined cycles. The pages keep battery-electric models from model year 2024 through the newest year in the file, group trims of the same make and model, and publish the median combined value for the newest year. There are 98 models after that cut. The price you pay for those kilowatt-hours is separate: a home rate, a public rate, and, where a utility has published one, an off-peak rate.

From kWh per 100 miles to a bill

Combined kilowatt-hours divided by 100, times miles, is energy. A vehicle at 30 kWh per 100 miles uses 3,000 kilowatt-hours to travel 10,000 miles. Ten thousand miles is the starting value in the calculator, so a full year is visible before you change it to your own mileage. The vehicles file is an energy rating. Miles are the figure you set.

At the 2025 U.S. residential average of 17.23¢ per kilowatt-hour, from EIA-861, 3,000 kilowatt-hours cost $516.90. A vehicle at 25 kWh per 100 miles uses 2,500 kilowatt-hours over the same 10,000 miles, or $430.75 at that rate. A vehicle at 40 uses 4,000 kilowatt-hours, or $689.20. The spread across the 98 models is the spread in the fueleconomy.gov combined ratings. Each model page names the fueleconomy.gov listing, the trim at the median, the city and highway ratings, and the range on that trim when the file includes one.

The home-rate box starts at 17.23¢ so the page opens on a documented national average. Replace it with your utility's price before you treat the dollars as a budget. Duke Energy Carolinas in North Carolina averaged 13.41¢ in 2025. At that rate the 3,000-kilowatt-hour example is $402.30. Hawaii's 2025 residential average is 40.40¢, and the same 3,000 kilowatt-hours are $1,212.00. The vehicle stayed the same. The EIA state price changed. The model page shows the national rate. The calculator is where a state price or a tariff goes.

Public charging

Public charger prices vary by network, city, and session. The fueleconomy.gov file is an energy rating, and the EIA-861 residential average is a home-customer average, so the calculator's public box starts at the same 17.23¢ and waits for the cents per kilowatt-hour on a receipt you have seen. A session fee or an idle fee sits outside that multiplication. If the charger bills by the minute, convert the session to cents per kilowatt-hour from a receipt you understand, then type that rate. The box is there for the price you actually paid.

Off-peak is a published window

Seattle City Light's residential time-of-use energy prices, effective January 1, 2026, for the city of Seattle, are 16.10¢ peak, 14.09¢ mid-peak, and 8.05¢ off-peak. Off-peak is midnight to 6 a.m. Peak is 5 p.m. to 9 p.m. Monday through Saturday, excluding city-observed holidays. The other hours are mid-peak. The flat residential schedule is $0.3945 per day plus 13.38¢ per kilowatt-hour. Suburban jurisdictions have their own schedules. The Seattle off-peak price applies to Seattle.

Charge 3,000 kilowatt-hours entirely off-peak at 8.05¢ and the energy is $241.50. Charge them on peak at 16.10¢ and the energy is $483.00. The difference is $241.50, which is 3,000 times the 8.05¢ gap. That comparison prices energy, and it holds when every kilowatt-hour of charging falls in the named window. The flat schedule's $0.3945 daily charge belongs to the flat option. A car that starts charging at 1 a.m. and is still charging at 7 a.m. has left the off-peak window under Seattle's definition. The kilowatt-hours after 6 a.m. are mid-peak, at 14.09¢, until the next period starts.

Other utilities publish other windows. A Texas time-of-use plan in the October 10, 2026 Power to Choose file is marked with a flag. Ninety-three rows carry that flag, out of 1,857. The hours are on the electricity facts label. The off-peak price to type is the one on that label. The 1,000-kilowatt-hour disclosed average already reflects the weighting the provider used. The off-peak line is the off-peak line.

Gasoline is a third number you set

The gasoline price on the calculator is EIA's U.S. regular grade, all formulations, retail, $4.354 per gallon for the week of October 5, 2026. The workbook's contents sheet dates that release October 6, 2026. Miles divided by the MPG you type is gallons. Gallons times $4.354 is the fuel cost. You choose the gasoline car. A 30-mile-per-gallon car over 10,000 miles uses 333.33 gallons. At $4.354 that is about $1,451.32. Set next to $516.90 of electricity at 17.23¢ and 30 kWh per 100 miles, the gap is the arithmetic of those inputs. Change the MPG, the electric rate, or the kWh per 100 miles and the gap changes. The $4.354 price is the national price for that week.

Charging at home on a flat rate

Where you are on a flat schedule, the home price is that schedule or the EIA average, labeled. Florida Power & Light's October 2026 peninsular insert is 12.258¢ for the first 1,000 kilowatt-hours and 14.258¢ above that, plus $10.52, before gross receipts tax and franchise fees. An EV that adds 300 kilowatt-hours to a month that was already at 1,000 pays the higher block on those extra kilowatt-hours. Three hundred times 14.258¢ is $42.77. The $10.52 was already on the bill. The same 300 kilowatt-hours on a month that was at 200 kilowatt-hours falls inside the first block, at 12.258¢, or $36.77. The insert's tiers are why the rate depends on the rest of the house. The EIA annual average of 14.62¢ for Florida Power & Light in 2025 folds that tier, the fixed charge, and the year into one cents figure. Use the insert when you are on RS-1 and you know which block you are in. Use 14.62¢ when you are describing 2025.

The model pages stay with the fueleconomy.gov rating and the national EIA price so every vehicle shares the same denominator. The calculator is the place to move the denominator to a tariff, to Seattle's 8.05¢ off-peak window, or to a public price you typed from a receipt.

City and highway ratings are on the model page because a highway trip can differ from the combined test. The combined value is the one multiplied by miles. If you drive a larger share of highway miles than the combined test assumes, the highway kWh per 100 miles is the closer rating, and both ratings are printed so you can see the split. Range, when the file has it, is the range on the median trim. Ninety-eight models is the count after keeping battery-electric vehicles from model year 2024 onward and collapsing trims. A trim that is not the median is inside the variant count on the page. The page URL is the model. Home charging at a flat rate, home charging in a named off-peak window, and public charging at a receipt price are three different bills for the same miles. The model page holds the energy rating steady so those prices can be compared on the same car, at the miles you actually expect to drive over a full year. Change the rate before you treat the dollars as next year's charging budget.