Home EV Charging Cost per Mile vs Gas: How to Calculate Your Savings

Charging an electric vehicle at home usually costs less per mile than fueling a comparable gasoline car, and the gap is largest when you charge off-peak on a home electric rate rather than at a public fast charger. You can calculate your own number in two lines: cost per mile for an EV is your electricity price in dollars per kWh multiplied by the kWh your car uses per mile, and cost per mile for gasoline is the price per gallon divided by the car's miles per gallon. This guide shows the arithmetic, a worked comparison with illustrative prices and how those savings determine whether a charger installation pays for itself.

The two formulas

EV cost per mile = electricity price per kWh x kWh per mile

Efficiency is often listed as miles per kWh or kWh per 100 miles. Convert as needed: a car rated at 3.5 miles per kWh uses 1 / 3.5, about 0.286 kWh per mile. The U.S. EPA publishes efficiency ratings for every model on fueleconomy.gov. Also include charging losses: when you charge from the wall, roughly 10 to 15 percent of energy is lost as heat in the charger and battery, so a rough rule is to multiply by 1.1 to 1.15 for wall-to-wheel cost. Some listed ratings already account for wall energy, so check the label basis.

Gas cost per mile = price per gallon / miles per gallon

Worked example with illustrative prices

These prices are examples for the arithmetic only. Replace them with your own utility bill and local gas price.

• Home electricity: 0.17 dollars per kWh (illustrative)
• EV efficiency: 0.29 kWh per mile at the wall
• Gasoline: 3.50 dollars per gallon (illustrative)
• Comparison car: 30 miles per gallon
• Public DC fast charging: 0.45 dollars per kWh (illustrative)

Results:

At 12,000 miles a year, home charging comes to about 12,000 x 0.049 = 588 dollars, gas about 12,000 x 0.117 = 1,404 dollars, and public fast charging about 12,000 x 0.131 = 1,572 dollars. The home advantage is about 816 dollars a year versus gas in this example, and the difference against heavy public fast charging is about 984 dollars. Notice that a driver who relies mainly on expensive fast charging may pay as much per mile as a gasoline driver, which is why home charging is the key to EV savings.

What changes your numbers

1. Your electric rate. Rates vary a lot across the country and across rate plans. A time-of-use plan with a cheap overnight window can cut the per-kWh price notably.
2. Tiered or demand pricing. Some tariffs charge more as monthly usage climbs; check whether adding an EV pushes you into a higher tier, and whether an EV-specific plan exists.
3. Vehicle efficiency. Larger vehicles and highway driving use more kWh per mile, and cold weather can raise consumption.
4. Charging losses. Level 1 charging can be slightly less efficient than Level 2 because of the fixed overhead of the charger running for more hours.
5. Gas price swings. Gasoline prices move more than regulated electricity rates, so your savings in any year will vary.

Turning savings into payback on the install

The installed cost of a charger is the up-front price of getting these savings. Suppose installation costs 1,800 dollars, a utility rebate is 250 dollars, and the net is 1,550 dollars. If, compared with your previous fueling, home charging saves 600 dollars a year, simple payback is 1,550 / 600, about 2.6 years. If your saving is only 250 dollars a year because you used free workplace charging, payback stretches to 6.2 years. The payback calculator lets you test these inputs, including a yearly change in savings.

Be careful about the comparison baseline. If you would not have paid for public charging anyway because you would have used Level 1 at home, the incremental savings of Level 2 is just convenience and time, not dollars. In that case the question becomes whether the speed is worth the cost. See is a home charger worth it.

Steps to calculate your own annual saving

1. Estimate yearly miles from your odometer or past service records.
2. Find your vehicle's efficiency on fueleconomy.gov and adjust for charging losses.
3. Compute kWh per year = miles x kWh per mile.
4. Multiply by your all-in home rate, including delivery charges, from your utility bill. Use the total cost per kWh, not only the supply portion.
5. Compute gas cost for the same miles using your previous car's mpg and your local price.
6. Subtract. That is your yearly saving versus gas.
7. If you also use public charging, compute that share separately and weight it.

Other costs to remember

Home charging cost per mile is not the only difference. Maintenance, registration fees for EVs in some states, insurance and depreciation all vary. A fair full-cost comparison includes them, but this guide isolates the energy cost because that is what the charger installation affects directly.

When to consult a professional

For tax or financial decisions that depend on your savings, such as whether to finance a project, talk with a qualified professional. For an electricity plan comparison, your utility's rate page and public utility commission list the options.

Frequently asked questions

Does charging at home raise my electric bill a lot?

It raises it by the kWh the car uses. Driving 12,000 miles at 0.29 kWh per mile is about 3,480 kWh a year, about 290 kWh a month in this example. Multiply by your rate to see the increase.

Is public Level 2 cheaper than fast charging?

Often, but pricing varies by network, venue and time. Check the station's displayed price before you plug in.

What is a good all-in electricity rate?

There is no universal figure. Look at your last bill, divide total dollars by total kWh, and compare with any EV or time-of-use plan your utility offers.

Sources

• FuelEconomy.gov — EPA efficiency ratings for EVs and gasoline vehicles
• U.S. Energy Information Administration — electricity and gasoline price data
• U.S. Department of Energy Alternative Fuels Data Center — home charging costs and rates