BMW i3 Vs Chevrolet Volt: Compare Cars
2015 BMW i3 REx – Driven, Portland OR, April 2015
The BMW i3 and Chevrolet Volt are two very, very different approaches to offering an electric car with a gasoline range extender. The little BMW is a battery-electric vehicle offeri— a small two-cylinder “REx” range-extending engine as an option for around $4,000 — the sole electric car in the world that can be ordered with or without an engine. The Volt, on the other hand, is closer to a plug-in hybrid—but it drives entirely on electricity until the battery is exhausted, just like the BMW.
Launched in May 2014, the electric BMW is one of the most advanced vehicles of any kind sold in the U.S. Its subcompact five-door body shell is made of carbon-fiber reinforced plastic, and it rides on an aluminum chassis that contains the battery pack, electric motor, range extender, and the crash structures. It’s light, custom-built, and the most efficient vehicle of any kind sold this year (in its battery-only form).
The Volt is in its fifth and final model year; it’ll be replaced with an all-new 2016 model. It’s a compact five-door hatchback with only four seats, and its construction is largely conventional. While the styling is distinctive, it’s nowhere near as unusual or futuristic looking as the little BMW, with its contrasting black panels.
Inside, the BMW i3 has a low, wide dash with a rectangular display screen sitting above it, and another screen in the instrument cluster that again sits above the dash surface. Its design theme is akin to Scandinavian modern, with some organic shapes and optional raw-wood appliques over some of the hard-plastic panels. The Volt interior is tighter and more cockpit-like, and its capacitive touch switches on the shiny-plastic center console have been the source of grumbling among owners.
But it’s the powertrains that set these cars apart. The Volt’s 111-kilowatt (149-horsepower) motor turns the front wheels by drawing power from a T-shaped lithium-ion battery pack that occupies the tunnel between the seats and some space behind the rear seat. Its capacity has risen steadily over the years: 2011 and 2012 models had 16.4 kilowatt-hours, 2013 and 2014 models had 16.8 kwh, and the 2015 model rose again, to 17.4 kwh. The Volt’s electric range was rated at 35 miles for the first two years, and 38 miles for the last three, although 2015 cars are likely to get more like 41 miles — GM just didn’t bother with the expense of retesting the car in its final year.
The BMW i3 has a 22-kwh lithium-ion battery under its floor, powering a 130-kw (170-hp) motor that turns the rear wheels. The REx range-extended version is rated at 72 miles on battery, and roughly the same again from its tiny 1.9-gallon gas tank. It’s heavier than the battery-electric version, which comes in at 81 mpg. Its efficiency is rated at 117 MPGe when in electric mode, and 39 miles per gallon when running on the range extender — versus 98 MPGe and 37 mpg for the Volt. (Miles Per Gallon Equivalent, or MPGe, is a measure of how far a car can travel electrically on the same energy that’s contained in a single gallon of gasoline.)
The two cars both drive like electric cars up to the limits of their batteries. Then each of their engines kicks in, in each case turning a generator that sends power to the traction motor through the battery pack — and recharging the battery just enough to provide a bit of an energy buffer, but not trying to recharge it beyond that. The Volt behaves rather like a hybrid in that mode, with the engine switching off at extended stops and the car moving away under electric power before the engine comes back on again. The BMW i3 keeps its engine on far more often once it’s in range-extending mode, but because the little motorcycle engine is behind the passengers, under the rear deck, it’s not as apparent. It sounds rather like a little motorboat engine in the distance, actually.
The BMW i3 REx has one major and important concern, however. Under the heaviest power demands, its engine may not be able to provide enough output to sustain the car. On rare occasions, for instance at high speeds on uphill stretches, carrying heavy loads and with all the climate controls working to overcome cold temperatures, the car may drop from freeway speeds to as little as 45 mph until its engine catches up and restores enough energy to the battery that it can resume full speed. It’s rare, but it does happen.
That aside, the tougher competition will be between the five-seat 2016 Volt — with its 50 miles of range — and the BMW i3 REx. This year’s Volt starts at about $35,000, with the BMW i3 REx roughly $10,000 more.