2014 BMW i3 REx Vs Chevy Volt: Range-Extended Electric Cars Compared

Until recently, the Chevy Volt was the only range-extended electric car available in the U.S.

I've driven a Volt for almost three years now, and it's been a splendid car--quiet, smooth, peppy, and amazingly economical.

New REx on the block

But now the Volt has a formidable new competitor: the new 2014 BMW i3, available as both a pure battery-electric vehicle or with an optional range-extending gasoline engine, known as the REx model.

Such a range-extended electric car, or series hybrid, has an electric motor that drives the wheels, plus a back-up gasoline-powered generator to provide electricity to run the car once the battery is depleted.

DON'T MISS: 2014 BMW i3: What A Tesla Driver Thinks Of New Electric BMW

A few weeks ago, I test-drove the pure-electric i3--and found it somewhat underwhelming compared to my Tesla Model S. 

But that's admittedly an unfair fight against an opponent with a price tag some $40,000 higher. By Model S standards, virtually any car is underwhelming.

2014 BMW i3 REx vs Chevrolet Volt comparison [photos: David Noland, Tom Moloughney]

2014 BMW i3 REx vs Chevrolet Volt comparison [photos: David Noland, Tom Moloughney]

The Volt-vs-i3 REx comparison, however, is legit. Both cars are compact four-seat four-door hatchbacks, and the price gap is only about $10,000--within the bounds of many cross-shoppers.

So how do the world's only two current-production range-extended electric cars measure up head-to-head?

Owners trade cars

Last week, BMW i3 REx owner and electric-car advocate and blogger Tom Moloughney and I got our cars together for a showdown.

We traded rides, drove the cars in close formation for about 30 miles in a variety of conditions, compared acceleration and handling,  and clambered in and out of back seats to compare foot- and head-room.

Tom rendered his verdict this morning. In my eyes, the winner of our grand REx smackdown was....well, it all depends.

Different philosophies

Although both Volt and i3 are classified as range-extended electric cars, Chevy  and BMW engineers came to their drafting boards with very different marching orders from management.

The Volt has an EPA all-electric range of 38 miles, enough to cover about 80 percent of typical daily commutes, according to GM. The 84-hp range-extender engine is designed to kick in regularly and provide full performance under almost all conditions. The driver doesn't need to know (or care) whether the REx engine is on or off.

Long cross-country trips?  No problem, gas range is 300-plus miles. Drive it like any other car.

The i3 REx, on the other hand, has an EPA all-electric range of 72 miles, good for perhaps 95 percent of daily trips. The much smaller 35-hp range-extender engine is meant to be used only rarely. Performance is limited in REx mode, so the driver needs to pay attention.

ALSO SEE: 2014 BMW i3 Electric Car: Why California Set Range Requirements, Engine Limits

And, for obscure regulatory reasons, the i3 has only a two-gallon gas tank, allowing  just 78 miles of gas range after the battery is depleted. On a long cross-country trip, you'll be stopping every hour or so to fill up.

According to BMW, "The range extender is not intended for daily use. It's for situations when the driver needs to extend the range of the vehicle to reach the next charging station. Therefore, the i3 probably won't be the choice for customers with a need for an extended range."

2014 BMW i3 REx owned by Tom Moloughney

2014 BMW i3 REx owned by Tom Moloughney

So let's see how these two widely divergent philosophies manifest themselves in the driver's seat.

Electric efficiency

During our face-off, Tom and I did a fairly extensive comparison of the cars' efficiency. We drove about 30 miles in trail, so that speed, acceleration, terrain, and traffic conditions were identical. Our route was about half city/suburban at speeds of 30-40 mph with lots of stoplights, and half Interstate cruising at 70-75 mph.

The official EPA efficiency numbers are 98 MPGe for the Volt and 117 MPGe for the i3. EPA electricity consumption numbers are 35 kWh per 100 miles for the Volt, and 29 kWh/100 mi for the i3.

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