Compare energy cost on the same distance
Gasoline energy cost per mile is the price per gallon divided by miles per gallon. EV charging energy cost per mile is electricity consumed per mile multiplied by the blended price per kWh. If your efficiency data is in miles per kWh, the calculator converts it to kWh per mile by taking the reciprocal. Keeping the distance basis consistent prevents a common error: comparing a gallon price directly with a charging session total.
The blended electricity price weights the home rate and public charging rate by the percentage of charging you assign to public charging. For example, a 20% public share combines 80% home charging and 20% public charging. This is a simple average; it does not distinguish time-of-use periods, subscriptions, session fees, idle charges or charging losses. Use a representative cost rather than assuming every public charger has one price.
Worked example with hypothetical values
Suppose a gas car gets 30 miles per gallon and gasoline costs $3.50 per gallon. Its energy cost is $3.50 ÷ 30 = about 11.67 cents per mile. A hypothetical EV using 0.30 kWh per mile, charging 80% at 18.16¢/kWh and 20% at 40¢/kWh, has blended electricity cost of 0.8 × 18.16 + 0.2 × 40 = 22.528¢/kWh. Its energy cost is 0.30 × 22.528 = about 6.76 cents per mile. At 12,000 miles annually, the model estimates about $1,400 in gas energy and $811 in EV electricity. These are arithmetic examples, not vehicle test results or a savings promise.
Annual difference and purchase-price recovery
The optional maintenance difference is entered as an annual dollar amount, positive when the user wants to count an EV maintenance advantage and negative values are rejected for this simple field. Annual operating difference equals the per-mile energy-cost difference times annual miles, plus that maintenance input. If the resulting annual difference is positive, simple recovery time divides the entered purchase-price difference by that annual amount; if you enter a negative price difference because the EV costs less, recovery shows 0 years. If annual operating costs do not favor the EV under the entries, the calculator reports that the purchase gap is not recovered. The calculation excludes financing, insurance, taxes, registration, resale value, battery condition, home charging equipment and the value of different vehicle features.
Efficiency and charging details
FuelEconomy.gov reports EV efficiency in formats such as kWh per 100 miles and MPGe. Convert kWh per 100 miles by dividing by 100 to obtain kWh per mile. Real-world use can differ with speed, terrain, temperature, cabin heating, tires and driving style. Charging losses mean the electricity billed at the meter may exceed the energy stored in the battery, so vehicle efficiency figures and household meter usage may not align exactly. Cold weather can affect range and energy use; this tool does not model those effects.
AFDC describes common home charging options including 120-volt Level 1 and 240-volt Level 2 equipment. Public DC fast charging is often priced differently from home electricity. Apply your own usage mix and tariff. Federal clean-vehicle credits are not assumed: the IRS says the credits apply only to vehicles acquired on or before September 30, 2025. Check the IRS directly for current details rather than relying on an old dealer advertisement. Mistakes include reversing miles/kWh, mixing cents and dollars, and treating a short public-charging sample as a full-year average. See the EV cost-per-mile guide for more context.