2014 BMW i3 REx range-extended electric car owned by Tom Moloughney - in dealership showroomEnlarge Photo
While the Tesla drives like an ingot on rails, I found the i3's steering slightly nervous, requiring tiny adjustments even on smooth, straight roads.
BMW fans and driving-glove/heel-and-toe types may view this highly sensitive steering feedback as a good thing. I can see their point, but I don't agree.
*The i3 has no battery percentage-state-of-charge indicator.
I was disappointed by this. The i3 has only a vague horizontal bar divided into quarters. At least that's better than the Model S, which has no delineation at all on its battery state-of-charge bar.
*Efficiency was surprisingly mediocre during my two test drives.
With temperature in the 70s and a mix of moderately aggressive driving (60 to 70 mph on four-lane suburban roads, 30 to 40 mph two-lane city streets), I averaged just 3.7 miles per kilowatt-hour, according to the car's panel readout.
Window sticker from 2014 BMW i3 battery-electric car, showing EPA ratings [photo: Tom Moloughney]Enlarge Photo
(I should note that I drove in "Comfort" mode, which provides full performance and climate control. Two other "Eco Pro" modes restrict these features to improve efficiency.)
A reading of 3.7 mi/kWh is the equivalent of about 270 watt-hours per mile, which is the unit the Tesla uses for its efficiency display.
Just a few days previously, I'd completed a 60-mile round trip in the Tesla, under similar temperature, speed, and road conditions, and averaged 290 kWh/mile.
It is astonishing and disappointing to me that the i3 would be only about 7 percent more efficient than a car that's nearly twice as heavy.
My efficiency number for the i3 correlates exactly with the EPA figure for the car, which is 27 kWh/100 miles. (To compare kWh/100 miles to Wh/mi, multiply by 10.)
But we must remember that the EPA efficiency rating is an out-of-the-wall-plug number that takes into account charging losses, which are typically 10 to 15 percent.
2014 BMW i3 electric cars waiting at East Coast shipping port for distribution, May 2014Enlarge Photo
So the EPA number implies that the i3 should use about 240 wH/mile from its battery, on average. My test-drive number of 270 was a bit worse than that.
On the other hand, my real-world results for the Model S after 20,000 miles are better than its EPA number. The Tesla's official rating is 38 kWh/100 miles, or 380 Wh/mi.
That translates to about 340 Wh/mi from the battery. I have used an average of 330 Wh/mi over those 20,000 miles, ranging from roughly 290 in the summer to 370 in the winter.
EPA arcana aside, my brief first-hand experience seems to indicate that the i3 is only slightly more efficient than the much larger and more spacious Tesla.
For a second opinion, Tom Moloughney, a pioneering BMW i3 owner and blogger, has reported an average consumption of about 220 Wh/mi after 1,500 miles of driving his i3--most of those miles apparently in Comfort mode.
I can't explain the discrepancy between his 220 and my 270. Perhaps he's a more conservative driver than I am.
Or perhaps experienced electric-car owners develop a "feel" for driving our cars efficiently that can't be matched during a quick test drive in a new car.
The surprisingly small efficiency advantage I found of the i3 over the Model S may not be quite so surprising once you look at the i3's aerodynamics.