How to Compare Gas and EV Energy Costs Fairly

A useful comparison holds annual mileage constant and changes only the vehicle efficiency and the price of its energy.

Calculate gasoline from miles and MPG

Divide distance by miles per gallon to estimate gallons, then multiply by the price per gallon. At 12,000 miles, 30 MPG, and $3.50 per gallon, the calculation is 400 gallons and $1,400. Rated MPG can differ from your real driving, especially with heavy traffic, cold weather, hills, or a fully loaded vehicle. Use a recent average from actual fill-ups when available.

Calculate electricity using kWh per 100 miles

EV efficiency is often shown as kilowatt-hours per 100 miles. At 30 kWh per 100 miles over 12,000 miles, the vehicle consumes an estimated 3,600 kWh before charging losses. At $0.17 per kWh, that is $612 without losses. With a 10% charging-loss assumption, grid purchase becomes 3,960 kWh and the arithmetic is $673.20. Home and public charging can have very different rates; a time-of-use plan can change the value further.

Keep the comparison narrow and honest

The gas-versus-EV tool compares energy spending only. It does not claim that one vehicle has a lower total cost of ownership. Purchase price, finance charges, depreciation, insurance, tire replacement, maintenance, and taxes may outweigh an energy difference. The U.S. Department of Energy vehicle cost calculator is a useful reference when you want a broader comparison.

Include commuting patterns

If a commute is 30 miles round trip, five days a week for 48 weeks, that is 7,200 commute miles a year. At 30 MPG and $3.50 per gallon, fuel alone is $840. Parking at $8 per workday adds $1,920, making a combined $2,760 before tolls, maintenance, and depreciation. The calculation is sensitive to work-from-home days and the number of weeks actually traveled.

Run a low, middle, and high price scenario when comparing vehicles. Record where every rate came from and when it was checked. A single national average may be convenient for a demonstration, but local receipts and utility bills make a better decision input.

Find the right rate on a bill or receipt

A gasoline price from one station on one day is a snapshot. If you are making a multi-year vehicle decision, test a range rather than assuming the latest receipt will stay constant. Electricity bills may include fixed charges, tiered rates, time-of-use periods, and taxes. A household’s average bill divided by all kWh is not always the price of the next kWh used for charging. Check the tariff or a measured charging session when possible.

If you rely on public charging, estimate what share of miles will use that network and its price. The simple EV tool uses one rate and a charging-loss assumption; you can run it twice for home and public charging, then combine the results according to your expected charging mix.

Compare total ownership only with fuller data

An energy-cost saving is a useful piece of information, but it is not an ownership saving by itself. A vehicle kept for three years and sold can have a different depreciation pattern from one kept for ten. Insurance quotes are personal, and financing terms matter. For a serious purchase comparison, gather the actual vehicle prices, incentives for which you qualify, annual insurance quotes, financing terms, service expectations, and resale assumptions.

Keep fuel and electricity arithmetic separate from those other estimates so you can see which number changed. If one scenario depends on unusually cheap electricity or optimistic MPG, mark it as such. A good comparison is reproducible by someone who sees your miles, efficiency, rates, and time horizon.

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