EV vs Gas Cost Calculator: What Each Car Costs Per Mile

Switching from a gasoline car to an electric one changes a recurring cost that most drivers never measure directly: the price of moving one mile. Gasoline is sold by the gallon and burned at an efficiency you rarely think about. Electricity is sold by the kilowatt-hour and consumed at a rate that varies with speed, temperature and driving style. This calculator puts both on the same footing, converts them into an annual number, and shows the difference.

The comparison it makes is deliberately narrow. It compares the running cost of two cars you might drive over the same year: the energy each one uses, plus a maintenance difference you supply. It does not compare purchase prices, loans, insurance or depreciation. Those are large, they vary enormously by vehicle and buyer, and mixing them into an energy calculation hides the part you can actually measure.

Read the result as a running-cost gap, not as a verdict on whether to buy. The gap is usually the most stable and predictable piece of the decision, which is exactly why it is worth isolating.

#The formula

The whole model rests on two cost-per-mile figures and one adjustment.

Formula: Gasoline cost per year = (annual miles / MPG) x price per gallon. Electricity cost per year = (annual miles x kWh per 100 miles / 100) x price per kWh. Annual difference = gasoline cost - electricity cost + extra gas maintenance.

Every symbol:

• Annual miles is total distance driven in a year, the same figure for both cars.
• MPG is the gas car's real-world fuel economy in miles per gallon.
• Price per gallon is what you actually pay at the pump, taxes included.
• kWh per 100 miles is the EV's energy consumption measured at the wall or at the plug, not the battery.
• Price per kWh is your marginal electricity rate, entered in cents and divided by 100 to get dollars.
• Extra gas maintenance is the annual servicing cost you expect on the gas car and not on the EV: oil changes, filters, spark plugs, exhaust work.

Cost per mile follows directly. For gasoline it is price per gallon / MPG. For electricity it is (kWh per 100 miles / 100) x price per kWh. The five- and ten-year figures are simply the annual difference multiplied out, with no inflation and no discounting applied.

#A worked example, done by hand

Take a driver covering 12,000 miles a year. Assume the gas car averages 28 MPG, gasoline costs $3.40 a gallon, the EV uses 30 kWh per 100 miles, home electricity costs 17 cents per kWh, and the gas car needs $300 a year of servicing the EV does not.

1. Gallons burned: 12,000 / 28 = 428.57 gallons.
2. Gasoline cost: 428.57 x $3.40 = $1,457.14 a year.
3. Energy used by the EV: 12,000 x 30 / 100 = 3,600 kWh.
4. Electricity cost: 3,600 x $0.17 = $612.00 a year.
5. Gasoline cost per mile: $1,457.14 / 12,000 = $0.1214, or 12.14 cents.
6. Electricity cost per mile: $612.00 / 12,000 = $0.0510, or 5.10 cents.
7. Energy difference: $1,457.14 - $612.00 = $845.14.
8. Add the maintenance difference: $845.14 + $300 = $1,145.14 a year.

Over five years that is $5,725.70 and over ten years $11,451.40, holding every assumption fixed. Those multiples are the least trustworthy numbers on the page, because no fuel price or electricity rate stays still for a decade.

#Where each input comes from

Annual miles. Take two odometer readings a year apart, or read the mileage off consecutive service invoices. Guessing from a daily commute usually undercounts, because errands and trips add up. If your driving is mostly a fixed journey, the commute cost calculator builds the annual figure from days per week instead.

MPG. Use your own measured economy, not the window sticker. Fill the tank, reset the trip meter, drive normally, refill, and divide miles by gallons added. Repeat over three tanks and average. The fuel economy calculator does that arithmetic and converts between MPG and L/100km using L/100km = 235.215 / MPG.

Gasoline price. Use the price you actually pay, averaged over recent fills, not a headline national figure.

kWh per 100 miles. The car's trip computer usually reports this, or its inverse in miles per kWh. If you have a metered home charger, divide the kWh it delivered by the miles driven in that period and multiply by 100; that version already includes charging losses.

Electricity price. Divide the total dollars on a recent bill by the total kWh billed, including fixed charges spread across usage, rather than reading the headline energy rate. If you are on a time-of-use plan and charge overnight, use the off-peak rate. The electricity cost calculator walks through pulling a real rate off a bill.

Maintenance difference. Add up a year of oil changes, filters, plugs and exhaust or emissions work on the gas car. Tires, brakes, suspension, wipers and insurance apply to both cars, so leave them out. EVs are heavier and can wear tires faster, which is a reason to keep this number conservative.

The answer is most sensitive to electricity price and to MPG. A cheap-to-run gas car meeting expensive public charging can erase the gap entirely.

#kWh per 100 miles versus MPGe

MPGe converts an EV's electricity use into a gasoline equivalent using a fixed conversion of 33.7 kWh to one gallon of gasoline, the gasoline-equivalent figure used for US federal fuel-economy labelling and therefore for the number printed on a window sticker. It exists so that window stickers can show one comparable number, and it is useful for that.

It is close to useless for cost, because it deliberately discards price. A gallon of gasoline and 33.7 kWh of electricity cost wildly different amounts, and the ratio between them changes by region, by season and by whether you charge at home or in a parking garage. MPGe answers "how much energy," while your bill asks "how much money."

kWh per 100 miles is the number that multiplies directly by a price to give dollars. It is also easier to reason about: 30 kWh per 100 miles means every 100 miles adds 30 kWh to the meter.

The gasoline side moves the same way, driven by pump price and MPG:

Read the two tables together. A 50 MPG hybrid at $2.80 costs 5.60 cents a mile, which an EV only beats on cheap home electricity.

#Charging losses: wall energy versus battery energy

Not all the electricity that leaves the wall reaches the battery. Some is lost in the charger, in the on-board converter, in heating or cooling the pack during charging, and in the car's own standby draw between sessions. Typical round-trip losses on home AC charging run about 10 to 15 percent.

That matters because the number on the car's dashboard is often battery energy, while the number on your bill is wall energy.

Worked example: if the car reports 27 kWh consumed over 100 miles and charging is 88 percent efficient, the meter sees 27 / 0.88 = 30.7 kWh per 100 miles. At 17 cents that is 5.22 cents a mile instead of 4.59 cents, a difference of about 14 percent on the whole year.

If your consumption figure came from a metered charger or from comparing utility bills, the losses are already inside it and adding them again would double-count.

#Home charging versus public fast charging

This is the single largest swing in the model, and it is the reason two people with identical cars can reach opposite conclusions.

Home charging is billed at your residential rate. Public DC fast charging is a separate retail product with its own pricing, and it commonly costs substantially more per kWh than charging at home, sometimes with session fees or idle fees on top. How much more depends on the network, the location and the time of day, so look up what the chargers you would actually use are charging rather than assuming a multiple of your home rate. Someone without a driveway or a dedicated parking space may do most of their charging that way.

Those rates are illustrative, not quoted prices. Substitute what you are actually charged. The pattern is what matters: the advantage narrows steadily as the effective rate rises, and at a high enough rate against an efficient gas car it disappears.

#Cold weather, degradation and other drift

Cold weather raises consumption in two ways. Battery chemistry is less efficient below freezing, and cabin heating draws directly from the pack because there is no waste engine heat to reuse. A car averaging 30 kWh per 100 miles in mild conditions can reach 40 or more in a hard winter month. At 17 cents across a whole year at that rate, the same 12,000 miles would cost $816 instead of $612.

Gasoline cars also lose economy in the cold, from longer warm-up and denser air, but usually by a smaller proportion.

Battery degradation reduces usable range over time. It affects how often you charge and how much buffer you keep, more than it changes energy per mile. The running cost per mile is fairly stable as a pack ages; convenience is what changes.

Speed matters more than most drivers expect. Aerodynamic drag rises with the square of speed, so sustained highway driving pushes consumption up for both cars, though EVs feel it more sharply because they are so efficient at low speeds.

#How to read the result

The annual figure is a running-cost difference under your assumptions, not a prediction. Treat it as the size of the gap you would need to justify any price premium, not as money already in hand.

A useful move is to divide a purchase price difference by the annual saving. If one car costs $6,000 more and the modeled saving is $1,145 a year, that is roughly 5.2 years of driving before the energy and maintenance gap covers the difference, ignoring financing and resale entirely. The cost per use calculator applies the same reasoning to any durable purchase.

Run the calculation twice, once with pessimistic inputs and once with optimistic ones. If the sign of the answer flips between them, the honest conclusion is that running cost does not decide this for you.

#What this model leaves out

• Purchase price and financing. No vehicle price, down payment, loan term or interest. Compare monthly payments with the loan calculator.
• Depreciation. Usually the largest single cost of owning any car, and entirely absent here.
• Insurance. Premiums often differ between an EV and a comparable gas car.
• Tax credits, rebates and fees. Federal, state and utility incentives change, and several states charge EV registration surcharges to replace fuel tax.
• Home charger installation. A dedicated circuit is a one-time cost that varies with panel capacity and wiring distance.
• Time and inconvenience. Waiting at a charger on a long trip has a value that no per-mile figure captures.
• Solar self-supply. Charging from panels you already own changes the marginal cost of electricity; the solar payback calculator handles that separately.
• Price movement. Both fuel and electricity prices are held flat across the five- and ten-year projections.

#Common mistakes

Using sticker MPG instead of measured MPG. Real-world economy is usually below the rating, which understates the gas car's cost and, in this comparison, understates the EV's advantage.

Using the dashboard consumption figure as if it were wall energy. That skips charging losses of roughly 10 to 15 percent.

Using a headline electricity rate. Delivery charges, fixed fees and tiered pricing mean the effective rate is often well above the advertised energy rate.

Assuming home charging when you cannot charge at home. This is the error that changes the answer most.

Double-counting maintenance. Tires, brakes, wipers and insurance apply to both cars. Only the genuinely gas-only items belong in that field.

Reading the ten-year number literally. It is the annual figure times ten with no price movement and no ownership change. Treat it as a scale, not a forecast.

Comparing a small EV to a large truck. Hold vehicle class constant, or you are measuring the size difference and calling it a drivetrain difference.