The BMW i3 and Chevy Volt both are small plug-in electric cars, but the two cars tackle the range-extended electric vehicle question in very different ways.
The latest Chevrolet Volt is essentially a plug-in hybrid, but it's the only one on the market that drives entirely on electricity until the battery is exhausted. In that behavior, it's similar to the BMW i3, a battery-electric vehicle that offers an optional small, 2-cylinder "REx" range-extending engine for around $4,000 — the sole electric car in the world that can be ordered with or without an engine.
So which one should you buy—the refined new Volt, or the intriguing i3?
On our scale, the i3 ranks slightly higher, but there's a caveat. We're changing our ratings system this year, and haven't yet rated the 2017 i3 or its larger battery pack. When it's available for testing and rating, we'll update this page.
The all-new Chevrolet Volt is sleeker, better-looking, quieter, faster, and more refined than the first-generation car sold from 2011 to 2015. It remains a compact five-door hatchback with only four seats, though it now has a fifth "seating" position that's largely restricted to agile and tolerant teenagers willing to sit on a small padded hump and straddle the wide battery tunnel. The Volt's steel construction is largely conventional.
Launched in May 2014, the electric BMW is one of the most advanced vehicles of any kind sold in the U.S. It's light, custom-built, and the most efficient vehicle of any kind sold this year (in its battery-only form). The 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. For 2016, its sole changes are a handful of new color, though for 2017 it will add a higher-capacity battery pack.
The little BMW, with its contrasting black panels, is unusual, distinctive, and futuristic-looking. It's a tall, slab-sided hatchback with two long front doors, plus rear "carriage doors" that can't be opened unless the fronts are opened first--meaning back-seat occupants are dependent on the front-seat passenger to get in and out. The Volt is a low, wedge-shaped hatchback that some have compared to the last Honda Civic in its shape. Regardless, it's handsomer, racier, and altogether better-looking than its predecessor to most eyes.
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 more cockpit-like, but it's now quite conventional, with soft-touch surfaces and available two-tone upholstery treatments that convey a premium feel. The entire control interface shares a lot with other GM small cars--which, in this case, means it's well designed and intuitive for the most part.
But it's the powertrains that set these cars apart. 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 Volt now uses a 1.5-liter four-cylinder engine paired with the latest Voltec two-motor plug-in hybrid system. The 18.4-kWh battery pack in the tunnel and under the rear seat gives 53 miles of electric range before the engine switches on, up from the previous model's 38 mpg combined. When operating in range-extended mode, essentially as a hybrid, the 2016 Volt is rated at 42 mpg combined. In electric mode, its efficiency is rated at 106 MPGe.
Both cars behave like battery-electric vehicles up to the limits of their battery capacities. Then each car's engine kicks in. The i3's engine powers a generator that sends power to the traction motor through the battery pack — and recharges the battery just enough to provide a bit of an energy buffer, but not trying to recharge it beyond that. The BMW i3 keeps its engine on most of the time when 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 new Volt behaves more like a plug-in hybrid once its battery is depleted, with the engine switching off at extended stops and the car moving away under electric power before the engine comes back on again. Unlike the BMW, its engine will mechanically clutch in to drive the front wheels directly when its control software indicates that's more efficient than charging the battery, but all of that is entirely imperceptible to the driver and passengers. Engine noise is apparent but well muffled, and the driving responsiveness is that of an electric car.
The BMW i3 REx has one major and important caveat, 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.
It's also worth noting that the range-extended version of the BMW i3 (known as the REx) has a tiny gas tank of less than 2 gallons that has to be refilled every 65 to 75 miles. The Volt, on the other hand, has a combined battery and gasoline range of about 400 miles--meaning it's more practical for long-distance trips. (It's designed that way specifically to comply with specific rules in California, but the result is a drawback for those North American buyers who may want the car to cope with longer-distance road trips as well.)
The Volt starts at about $34,000, with the BMW i3 REx roughly $10,000 more. If you're looking for a mostly-electric car that eliminates the range anxiety of a battery-electric vehicle, they're the two best choices. If you're willing to sacrifice the prestige of the BMW brand, and overlook any negative perceptions of Chevrolet cars, the Volt may be the better way to find a vehicle that meets your needs.
The Volt is our choice, giving an excellent blend of conventional styling and interior with a smooth, powerful, advanced, and energy-efficient powertrain. The second-generation Volt retains all the good points of the first edition, while fixing some of the drawbacks and adding more range. The i3 scores better here for the moment, but we fully expect its ranking to drop once it's assessed on our new rating scale.
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