Gas vs Electric Cost Per Mile: How to Compare Fairly
- Gas cost per mile: price per gallon ÷ MPG.
- EV cost per mile: (kWh/100 miles ÷ 100) × price per kWh.
- Reality check: EV charging losses and charging location (home vs public) can change your average.
What We Know (Sourced)
EPA explains that MPG equivalent (MPGe) is used for plug-in electric vehicles and that it expresses energy consumption using the equivalent energy content of a gallon of gasoline. Source: U.S. EPA — Fuel Economy and EV Range Testing.
EPA’s electric vehicle label documentation explains that kilowatt-hours per 100 miles is an energy-use metric that relates directly to electricity used and therefore to cost. Source: U.S. EPA — Text version of the electric vehicle label.
EPA notes that MPGe values include charging losses so they represent energy use “from the wall.” Source: EPA testing documentation.
Choose the Right Metrics
There are three “official” efficiency numbers you’ll see most often:
- Gas car: MPG (City/Highway/Combined) from the EPA label.
- EV: MPGe (useful for cross-fuel comparisons).
- EV: kWh/100 miles (useful for charging cost).
For understanding the label layout and what each number means, start with: EPA label basics and the EV-focused explainers: MPGe and kWh per 100 miles.
Formulas (Gas and EV)
If you prefer a larger, comparison-friendly unit, use cost per 100 miles for both. Related guide: Fuel cost per 100 miles.
Step-by-Step Comparison
- Pick your driving baseline: use the EPA Combined MPG/MPGe as a starting point unless your driving is extremely city-heavy or highway-heavy.
- Set your local prices: $/gal for gas and $/kWh for electricity (home and/or public).
- Compute gas cost per mile from MPG and gas price.
- Compute EV cost per mile from kWh/100 miles and electricity price.
- Scale to your annual miles to estimate budget impact.
Use a calculator instead
Compare annual energy costs for a gas car and an EV with your own miles and prices.
Gas vs Electric Cost CalculatorWhat’s Next
Once you have cost per mile for both vehicles, you can answer “real” questions:
- Commute budget: multiply cost per mile by your weekly miles.
- Break-even analysis: estimate how long it takes for lower cost per mile to offset a higher purchase price.
- Sensitivity checks: see how results change if gas or electricity prices change.
Related guides: commute fuel budgeting and break-even MPG payback.
Why It Matters
EPA’s label and testing documentation makes clear that EV efficiency is reported in both MPGe (a gasoline-equivalent metric) and electricity-use units like kWh/100 miles. Those two views are exactly what you need for a fair cost-per-mile comparison: one common unit (dollars per mile) built from standardized efficiency and your local energy prices. Sources: EPA testing and EPA EV label text.
Frequently Asked Questions
Should I compare MPGe to MPG directly?
MPGe is designed to be MPG-like for cross-fuel comparisons, but cost comparisons usually work better using kWh/100 miles and your electricity price. MPGe is still useful when you want one efficiency number across fuels.
Do EV labels account for charging losses?
EPA notes that MPGe values include charging losses and are intended to represent energy use at the outlet. Source: EPA testing documentation.
Where do I find official kWh/100 miles values?
kWh per 100 miles is explained in EPA’s electric vehicle label documentation and appears in EV label materials. Source: EPA EV label text.