Gas vs Electric: The Four Numbers That Actually Decide It

“Gas or electric?” is usually argued with anecdotes and tribe. It’s actually a four-variable arithmetic problem with a definite answer for any two specific cars and your driving. This post identifies the four variables, shows how they combine, and gives you a calculator that settles it for your case rather than in the abstract.

The decision is not ideological

There is no universal answer to gas-vs-EV, which is exactly why the debate never ends — both sides are generalizing from their own four numbers. The honest framing: pick the two specific cars you’re choosing between, your real annual mileage, and your real energy prices, and total the lifetime cost of each. The cheaper one is cheaper. For someone else with different numbers, the other one is.

The total for each side:

gas total = price − resale + (miles/MPG · gasPrice)·years + upkeep·years
ev total  = (price − incentive) − resale
            + (miles · (1/eff)/(1−loss) · elecRate)·years + upkeep·years

Two things in the EV line deserve attention. The incentive is subtracted from the purchase price but resale is computed on the sticker (you can’t resell the tax credit). And EV energy is grossed up by (1 − loss) because charging isn’t 100% efficient — wall energy exceeds battery energy by roughly 10% on home Level 2. Casual EV math drops that term and understates running cost.

Run it for your two cars

The calculator also reports the payback on the EV’s price premium: if the EV costs more upfront net of incentive but less to run, how many years until the running saving repays the premium. If there’s no premium or no running saving, payback doesn’t apply and it says so.

The four numbers that decide it

1. Annual mileage. The EV’s per-mile energy advantage only accumulates if you drive enough miles. A low-mileage driver may never recover an EV premium; a high-mileage one recovers it fast. This is the single most decisive variable.

2. The energy-price gap. Cheap home electricity versus expensive gas is where the savings live. Charge at home off-peak and the gap is large; rely on public DC fast charging and it can vanish entirely — public rates often rival gas on a per-mile basis.

3. The net incentive. Incentives can erase the upfront premium — or not apply at all, depending on model, sourcing, your income, and purchase vs lease. Enter only what you’ll actually receive; a credit you can’t claim doesn’t belong in the comparison.

4. Resale. EV resale has historically been more volatile than mainstream gas cars (battery-life perception, fast technology turnover). A ten-point difference in retained value can outweigh years of fuel savings. It’s the most uncertain input and often the swing factor.

The EV question isn’t ideological. It’s mileage × energy-price gap × incentive × resale — four numbers, one answer, different for everyone.

What the model deliberately ignores

• Home-charger install cost. A one-time Level 2 install belongs on the EV side if you need one — see EV Charging Cost.
• Battery replacement. Rare within typical ownership but a genuine tail risk, not modeled.
• Financing interest. Compare cash-equivalent here; use the auto loan calculator for each car’s financing cost.
• Gas-price inflation and time-of-use tariffs. Use conservative figures for long horizons.

The one-paragraph version

Lifetime gas-vs-EV cost is purchase (EV net of incentive) minus resale, plus energy (EV energy grossed up for charging losses) and maintenance over your ownership period. Four numbers decide it: annual mileage, the home-vs-gas energy-price gap, the net incentive you’ll actually get, and each car’s resale retention. Run your two specific cars through the gas vs electric calculator instead of arguing the general case.

Related calculators

• Gas vs Electric Total Cost — lifetime cost of both, with premium payback.
• EV Charging Cost — the EV energy side, losses included.
• Fuel Cost — the gas energy side in detail.
• True Cost of Ownership — full cost of either choice.

AutoMath is an educational tool, not financial advice. Prices, rates, incentives, and resale values change — compare two specific cars on consistent assumptions.