BMW i8
The window sticker shows one number. This car has three — 27 MPG with a flat battery, 69 MPGe on electricity, and a blend of the two that assumes you drive 42% of your miles on the battery. Which one applies to you is decided by how often you plug in, not by the EPA.
Your cost per mile
Every version, 2020
| Version | Combined | City | Highway | Fuel | EPA annual |
|---|---|---|---|---|---|
| 1.5L 3cyl · AWD · Automatic 6-spd | 27 | 26 | 29 | Premium | $2,850 |
| 1.5L 3cyl · AWD · Automatic 6-spd | 27 | 26 | 29 | Premium | $2,850 |
2 configurations, 27–27 MPG.
Every model year
| Year | Gas only | MPGe | EPA assumes | Elec range | kWh/100mi |
|---|---|---|---|---|---|
| 2014 | 28 | 76 | 37% | 15 | 43 |
| 2015 | 28 | 76 | 37% | 15 | 43 |
| 2016 | 28 | 76 | 37% | 15 | 43 |
| 2017 | 28 | 76 | 37% | 15 | 43 |
| 2019 | 27 | 69 | 42% | 18 | 49 |
| 2020 | 27 | 69 | 42% | 18 | 49 |
Straight from the EPA certification database, one row per model year, showing the best-rated version of each. Trims with identical figures are collapsed.
What owners report
| Year | Owners | Average reported | Spread |
|---|---|---|---|
| 2015 | 1 | 99.9 | 100–100 |
One owner filed these through the EPA's own My MPG tool. That is a sample, not an average — read them as anecdotes. They are here because they are the only owner-reported figures in public federal data.
Across the EPA's plug-in data, owners have filed averages as high as 558 and even 1,174 MPG. Those are not typos. MPG is miles divided by gallons, and someone who charges every night buys almost no gasoline, so the divisor approaches zero and the number runs away. MPG cannot describe a plug-in hybrid. That is why the calculator above works in cost per mile.
How this is worked out
Your electric share is your daily electric miles over your daily miles, capped
at the 18-mile rated range per charge. That share is costed at the electricity
price and the rest at the gasoline price. The kWh figure is EPA's combE, measured
at the wall, so charging losses are already inside it — you are not paying for
them twice.
Every figure comes from the U.S. EPA's public fuel economy data. We add no estimates of our own; a missing number shows as a dash rather than a guess.
Add your numbers
Federal data has at most a handful of owners per car and nothing at all on servicing. If you own one, send what you actually get. It goes on this page with the sample size next to it.