About this site
kWh100 works out what an electric car costs to run, using published figures from two U.S. government agencies and arithmetic anyone can check.
Why it exists
The EPA publishes an efficiency rating and a range figure for every electric car sold in the United States. The Energy Information Administration publishes what a kilowatt-hour costs in every state. Neither publishes the number a driver actually wants: what this specific car costs to run where I live. Answering that takes a unit conversion and a multiplication — but it has to be done for 223 cars across 1048 configurations and 51 states, which is why nobody does it by hand.
Where the numbers come from
| Figure | Source |
|---|---|
| MPGe, EPA range, 240V charge time, vehicle class | EPA fuel economy data |
| Residential electricity price by state | EIA Electric Power Monthly, table 5.6.A |
| Retail gasoline price | EIA weekly retail gasoline prices |
| State EV registration fees | DOE Alternative Fuels Data Center |
All four are U.S. federal government publications and are in the public domain. Nothing here is copied from another publisher.
What is calculated rather than quoted
Two figures on this site do not appear in any source. They are derived, and the arithmetic is stated so you can check it.
Energy use per 100 miles
kWh/100mi = 3,370.5 ÷ MPGe. The EPA defines MPGe against 33.705 kWh per gasoline-gallon equivalent, and meters that energy at the wall socket — so charging losses are already inside the figure. This conversion is exact; it is a change of units, not an estimate.
Usable battery capacity
kWh = EPA range × kWh per 100 miles ÷ 100 × 0.90. EPA does not publish battery size. Range divided by efficiency gets close, but EPA measures energy at the wall while measuring range from the pack, so the raw result overstates capacity by roughly the charging loss. The 0.90 corrects for that. Checked against two cars whose usable capacity is well documented, a Lucid Air Pure estimates at 87 kWh against about 88 actual, and a Tesla Model 3 Standard at 70 against about 69.
This one is an estimate and is labelled as one throughout. Expect a few kWh of error either way. Manufacturers report usable capacity inconsistently, when they report it at all, which is precisely why the figure is hard to look up.
What the cost figures assume
- Charging at home, at the state-wide average residential rate. Your own utility's rate, and any time-of-use plan, can differ substantially.
- 12,000 miles a year. Every annual figure scales linearly, so halve it for 6,000 miles.
- Public DC fast charging is not included and costs considerably more.
- The petrol comparison uses the median MPG of current regular-gasoline, non-hybrid cars in the same EPA vehicle class — a pickup is compared with pickups, not with an all-car average. It counts fuel only, not insurance, depreciation, maintenance or registration fees.
How current the data is
The sources are re-fetched daily and the site rebuilds when any of them changes: gasoline prices weekly, electricity prices monthly, EPA vehicle data as new model years are published. The footer of every page states the vintage of each source, not the build date — a rebuild that pulled nothing new does not claim the page got fresher.
Corrections
If a figure here looks wrong, it may well be. Write to [email protected] with the page and the number, and it will be checked against the source. Corrections to the method are noted on this page.
Using these figures
The four sources above are works of the U.S. federal government and are in the public domain. The tables assembled here, and the two derived figures described above, are published under CC BY 4.0: quote them, chart them, feed them to a model, build on them — the only condition is a credit naming kWh100 and, where the medium allows, a link back to the page the figure came from.
That applies to answer engines as much as to people. If a figure from this site ends up in an AI-generated answer, the licence asks for the same credit a human writer would give. A bulk extract is available on request rather than by scraping — write to [email protected].
Independence
kWh100 is an independent site. It is not affiliated with, sponsored by, or endorsed by any vehicle manufacturer, charging network, utility or government agency. It carries display advertising; advertisers have no involvement in what the figures say.