A gas car's real range is roughly tank size (gallons) × combined mpg, minus a 10-15% reserve buffer most drivers keep — a 14-gallon tank at 32 mpg gives about 380-400 usable miles. An EV's real range is its battery capacity (kWh) ÷ efficiency (kWh per 100 miles), but that number swings 20-40% with speed, temperature and HVAC use — a 300-mile rated EV can realistically deliver 180-220 miles on a cold highway trip and 280-320 in mild city driving.
At a glance
| Factor | ICE range impact | EV range impact |
|---|---|---|
| Highway vs city speed | -10% to -15% at 75+ mph | -20% to -30% at 75+ mph |
| Cold weather (<32°F/0°C) | -5% to -10% | -20% to -40% |
| A/C or heater use | -2% to -5% | -10% to -20% |
| Heavy load / towing | -15% to -30% | -20% to -50% |
| Reserve buffer kept | 10-15% of tank | 10-20% of battery |
The basic ICE range formula
For a gasoline or diesel car, theoretical range = usable tank capacity × combined fuel economy. A 14-gallon tank rated at 32 mpg combined gives 448 miles on paper. In practice, drivers rarely run a tank to zero, and official combined ratings assume a mix of driving that doesn't match everyone's commute, so a realistic planning number is that theoretical figure minus a 10-15% buffer — around 380-400 miles for that example.
The two biggest swings for ICE range are driving style/speed (aerodynamic drag rises sharply above ~65 mph, cutting highway mpg by 10-15% versus the rated figure) and load (a full car plus a loaded roof box can cut range 15-20%).
The EV range formula — and why it's noisier
For an EV, theoretical range = usable battery capacity (kWh) ÷ energy consumption (kWh per mile or per 100 miles). A 75 kWh usable battery at 25 kWh/100mi gives 300 miles on paper. Unlike a fuel tank, though, an EV's real-world efficiency changes dramatically with temperature and speed because battery chemistry itself is less efficient in the cold, and because there's no 'waste heat' from a combustion engine to warm the cabin for free — the heater draws directly from the battery.
| Condition | Typical EV range vs. rated |
|---|---|
| Mild weather, mixed driving | 95-105% of rated |
| Highway at 75+ mph | 70-85% of rated |
| Cold (<32°F/0°C), heater on | 60-80% of rated |
| Cold + highway combined | 55-70% of rated |
How a good range estimator should ask questions
A range estimator that only asks for battery size or tank size and an EPA/WLTP-style rating is giving you a best-case number. A better tool asks about season, expected average speed, and whether you'll run climate control heavily — and applies a percentage adjustment on top of the rated figure rather than presenting the label number as a promise.
- Start with the manufacturer-rated range (EPA, WLTP or local equivalent) as the ceiling, not the expectation.
- Apply a speed adjustment: subtract roughly 1% of range per mph above 60 mph sustained highway speed.
- Apply a climate adjustment: subtract 15-30% in freezing conditions with cabin heating running.
- Apply a reserve buffer: plan to arrive with 10-20% remaining rather than running to empty, especially for EVs where charging isn't as universally available as fuel.
Worked comparison
Take a gas SUV rated 25 mpg combined with a 16-gallon tank (400 miles theoretical, ~350 practical with buffer) against an EV SUV rated 250 miles EPA. On a summer commute, both largely deliver their rated figures. On a winter highway road trip, the gas SUV might drop to 300-320 practical miles (a 10-15% hit), while the EV could realistically deliver 150-180 miles (a 30-40% hit) — which is why route planning and charging-stop buffers matter far more for EV trips than fuel stops do for gas trips.
Manufacturer-quoted EV range figures (EPA, WLTP) are tested under specific lab conditions. WLTP figures in particular tend to run 10-20% higher than real-world US-style EPA testing for the same car, so compare like-for-like ratings when cross-shopping between regions.
Frequently asked questions
Why does my EV's range drop so much in winter?
Is WLTP or EPA range more realistic?
Does towing affect EV range more than gas car range?
How much reserve should I plan for on a road trip?
Do range estimator apps account for elevation and terrain?
Sources & further reading
- U.S. EPA – Fuel Economy and EV Range Testing
- U.S. DOE Alternative Fuels Data Center – EV Range in Cold Weather
- WLTP Facts – Worldwide Harmonised Light Vehicle Test Procedure
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
