How to Calculate EV Charging Cost: The Formula We Use

EV charging cost is the electricity your car uses multiplied by the price you pay for it: cost per mile = (kWh per 100 miles ÷ 100) × your electricity rate in $/kWh, and a full charge costs the kWh drawn from the wall × that same rate. Use the EPA’s kWh-per-100-miles figure exactly as published, because it is measured at the wall socket with charging losses already inside it — a battery size or your car’s own energy readout leaves those losses out, so starting from either understates what the meter bills you.

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4.5¢

a mile to charge a Tesla Model Y at home at the US average rate, worked through below

A worked example on a real car

Take the 2026 Tesla Model Y Long Range RWD at the US average residential rate of 18¢/kWh. Two inputs, one multiplication, and everything else is scaling.

That’s the whole method. The multiplication is the easy part; the inputs are where it goes wrong.

Of the two, the rate moves the answer most. The same full charge costs $11.02 at the average rate in Idaho and $29.68 at the average in California, and nothing about the car changes in between. So put your own rate in: the calculator opens with the Model Y’s EPA figure already filled in.

Where the math usually goes wrong

Counting charging losses twice, or not at all

Some of the electricity you pay for never reaches the battery. It’s lost as heat in the cable and the car’s onboard charger. The EPA already counts that. Its own testing notes (Fuel Economy and EV Range Testing) say the ratings assume Level 2 AC charging and include the losses in the cable and onboard charger, which moves the measurement from the car to the wall outlet. So the EPA number goes into the formula untouched.

Numbers measured at the battery point the other way. A battery’s capacity, or the kWh your car’s screen says it took on, counts only what arrived, not what the meter billed. How big the gap is moves with temperature and charging speed, and we have no published figure for it, so this site never starts from either number.

Mixing the two up is the common mistake, and it runs both ways. Multiply a battery size or a readout straight by your rate and you leave the losses out, so you undercount. Add a loss factor on top of an EPA figure and you count them twice, so you overcount. We know the second one from experience: this site did exactly that once, on every running cost it published.

Using the wrong rate

The rate that matters is the one on your own bill, all in: the energy charge plus any delivery charges billed per kWh. Leave the delivery charges out and the answer looks better than your bill will.

Two rate structures change which number to use. On a tiered plan, charging adds kWh at the top of your usage, so price them at your highest tier. On a time-of-use plan, use the price for the hours you actually charge, not the daily average.

Pricing public fast charging like home

The formula doesn’t change at a public charger. The rate does, and so does the structure. DC fast charging usually costs more per kWh than charging at home, and each network sets its own prices: by operator, state, time of day and membership, and some add session or idle fees on top of the per-kWh price.

There’s no national public-charging price series to cite, so we don’t quote a typical figure. Put the price the station shows you into the same formula. The EPA figure is also a Level 2 AC measurement, so at a DC fast charger treat it as a guide rather than an exact measure.

Forgetting the cold

Cold weather raises the energy each mile needs. In AAA electric vehicle temperature testing, published May 2026, EVs at 20°F lost 35.6% of their efficiency against mild weather.

That isn’t a 35.6% cost increase. Efficiency is miles per kWh, so losing that share of it means each mile draws about 55% more energy. The Model Y’s $4.50 per 100 miles becomes about $6.99 at that temperature.

How this site computes its numbers

Every cost on this site, including all 34 cost-to-charge pages and the calculator, is the arithmetic above fed by the inputs below. Each says where it came from, including the ones that are ours.

Consumption. The EPA combined rating in kWh per 100 miles for one specific trim, read off fueleconomy.gov. Used exactly as published, with no loss adjustment, because it’s measured at the wall. EPA figures checked August 2026.

Full charge. Not a battery size. We multiply the EPA range by the EPA consumption: the energy it takes to cover the rated range, measured at the wall. Carmakers usually publish gross battery capacity, which includes a buffer that never takes a charge. Published examples put usable capacity 2% to 6% below gross (Recurrent Auto, EVKX and EVspecs model data, checked August 2026), and the gap is a per-manufacturer choice, so no single factor converts one into the other. Two EPA figures from the same test avoid the guess.

Electricity rate. 18¢/kWh, the US average residential price from the EIA Electric Power Monthly (table 5.6.A, May 2026), rounded from 18.44¢ because it’s a starting value you’re meant to replace. Every vehicle page also prices the car at 12.35¢ (Idaho, the cheapest state) and 33.25¢ (California, the most expensive large mainland market), from the same table and month. Hawaii is higher still at 52¢, a 4.2:1 spread from cheapest to dearest. Checked August 2026.

Charging efficiency. 100% on every figure the site publishes, because each one starts from an EPA rating with the losses already counted. No loss factor is applied anywhere. The calculator keeps a charging-efficiency setting under “Advanced”, set to 100%, for anyone working from a number their car measured at the battery.

Miles per year. 12,000, a round number near the US average that we use for illustration rather than cite. Monthly figures are a twelfth of the year, not a modelled month.

The gas comparison. A 30 MPG car, which is illustrative, at $4.05 a gallon from the EIA weekly US regular retail gasoline price (week ending 17 August 2026); EV cost per mile vs gas runs every tracked car against it. The “mid-pack EV” on the vehicle pages is an illustrative 30 kWh per 100 miles.

What’s left out. Every figure is energy only. No charger installation, no battery wear, no rebates, and no public-network prices or fees. The cold-weather figures above are used for explanation only; the AAA numbers were recorded in August 2026 and haven’t been re-checked since.

Rates move every month and ratings change with model years, so treat any average as a starting point and your own bill as the final word. If you spot a figure here that has drifted, tell us.