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]

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

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.

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

Either way you measure, it's an official EPA 20 percent efficiency advantage for the BMW--not surprising considering it weighs 900 pounds less than the Volt.

Miles/kWh readouts

To add to the unit-confusion, both the Volt and i3 read out their efficiency in yet a third unit: miles/kWh, the electric analog to mpg. Since that's what our cars were telling us, that's the unit we used in our test.

We began our side-by-side efficiency run from the parking lot of Tom's restaurant, Nauna Bella Casa, in Montclair, New Jersey. After 13.1 miles of stop-and-go suburban driving (average speed 22 mph), the Volt, leading the way with Tom at the wheel, had used 3.1 kWh of juice, which worked out to an average of 4.5 miles/kWh.

I followed in the i3, which at the end of the city/suburban run displayed 5.0 miles/kWh. (Unlike the Volt, the i3 obligingly reads out the final average.)

2014 Chevrolet Volt 5dr HB Instrument Cluster

Advantage: i3--but by a smaller margin (11 percent) than I had expected. Especially considering that this had been a stop-and-go city route, where the i3's weight advantage is more telling.

Would the sleek Volt close the gap on the boxy i3 on the highway, where air resistance rules?

Surprisingly, no. The Volt managed 3.5 miles per kWh on our 15.2 mile run along Interstate 80 and the Garden State Parkway, compared to 4.0 mi/kWh for the i3. The i3's advantage actually increased to 14 percent on the highway.

Overall numbers for both city/suburban and highway legs: 3.9 mi/kWh for the Volt, 4.5 for the i3.

Bottom line: in our little test, the range-extended BMW was 10-15 percent more efficient than the Volt.

And, yes, efficiency is a virtue in its own right. But how does it pay off on the bottom line in this case? In terms of dollars and cents, the i3's efficiency advantage is almost trivial.

Based on our own testing numbers, the i3's efficiency advantage amounts to about one-third of a penny per mile.

Savings over a year and 12,000 miles of driving: a cool $40.

2014 BMW i3 REx owned by Tom Moloughney

Electric performance

With their instant electric torque, both cars are spritely performers. But the i3 has a clear advantage in acceleration.

We didn't do timed 0-60 tests, but the factory numbers reflect what the driver feels when he stomps the "gas" pedal: Zero-to sixty in 9.0 seconds for the Volt, 7.7 seconds for the Bimmer. Pedal to the metal, the i3 is the clear winner.

But in normal around-town driving, at less than full throttle, the Chevy feels just as peppy as the i3--as long as the Volt is in Sport mode. Its more aggressive throttle mapping makes the Volt jump off the line from stoplights. I always, always drive my Volt in Sport mode.

In terms of top speed, the Volt gets the nod. It's electronically limited to 100 mph, while the i3 REx cuts off at 93 mph.

I've never driven my Volt faster than about 85 mph, but it seems to have decent reserve power at that speed. Likewise, Tom reports that his i3 REx has "plenty of punch above 85 mph."

Range-extended performance

The Volt suffers essentially no performance penalty in REx mode. The 84-hp gas engine is powerful enough to maintain full performance under virtually all conditions.

The one exception is very long, steep, fast uphill stretches of road--say, Interstate 80 from Denver to Silverthorne, Colorado.

For this situation, the Volt offers a solution: Mountain mode, which kicks on the range extender when there's still about 40 percent of battery charge remaining. The battery is thus able to help out the range extender to maintain full power up long, fast grades.

The i3's tiny two-cylinder 35-hp REx engine, which kicks in when battery charge falls to 6 percent, cannot maintain full performance under all conditions.

In low-demand driving (moderate speeds, short and not-too-steep hills), the REx provides the battery with all the power it needs to maintain the 6-percent level, or even charge up the battery a bit.

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

But at higher speeds, or on hills, the battery may be called upon to help out. After a few minutes of helping out, the battery state of charge may fall to near zero.

When that happens, the car goes into a "limp-home" mode that limits speed to about 40 mph. At that point, the driver must either limp home or pull over for a while to allow the REx engine to charge the battery back up above the limp-home threshold--or better yet, above the 6percent REx kick-in threshold.

Can the i3 REx engine really hack it?



In three years and 35,000 miles, I've never encountered a situation that came close to overpowering the Volt's engine. (The mountains in my neck of the woods are measured in hundreds of feet, not thousands.) The only time I ever used Mountain Mode was just to see how it worked.

But I was eager to try out the i3 in range-extended mode, with that little two-cylinder scooter engine humming away back there. Did it have the guts to maintain a safe, comfortable speed on the New York State Thruway?

2014 BMW i3

To my surprise, the answer was yes. Tom and I drove about 25 miles on the Garden State Parkway, New York State Thruway, and New Jersey Route 17, maintaining speeds of 60 to 65 mph as traffic allowed.

We weren't the fastest drivers on the road, but we weren't the slowest, either. At this quite reasonable speed, with a few brief uphill stretches here and there, the little i3 REx engine did a fine job of maintaining normal driving performance at the 6-percent battery charge level.

All the while a modest hum emanated from the back, at a steady cadence--unlike the Volt REx, which throttles constantly according to demand.

Ride and handling

Both Volt and i3 handle very well in normal day-to-day driving. But once again, there's a clear philosophical difference between the two cars.

The Volt has a smooth, solid, luxury-car ride. The steering is low-effort and vibration-free. It's a heavier car, and feels like it.

2014 BMW i3 hits the race track

The i3, on the other hand, is a BMW. The design philosophy is to keep the driver in intimate touch with the road. As a result, there's more feedback from the steering wheel, more vibration. It takes more effort to turn it.

If you're a BMW-type driver, you call this "sporty and responsive." If not, you might call it "jittery and a bit harsh."

I happen to fall, just barely, into the latter camp. I appreciated the i3's sporty, responsive feel. But I prefer the Volt's solid, smooth ride, especially at high speeds on the Interstate.

Performance handling

In terms of high-performance handling, I'm not qualified to evaluate either car. The only four-wheel drift I've ever done was in an icy parking lot at 20 mph. Heel-and-toe? I read about it once.

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

I did, however, get a brief, unintentional feel for the i3's high-performance handling. Cruising at 60 mph or so along New Jersey Route 17, I didn't notice our exit coming up until very late. Unfortunately I was in the middle lane, with another car directly to my right, blocking my way.

So I hit the "gas," and the i3 shot instantly forward. We then swerved sharply to the right in front of the other car and directly into the rather abrupt exit curve.

Even in my inexpert hands, the i3 handled it all with utter aplomb, with nary a wobble or squeal of tires.

Could the Volt have managed the same maneuver with such ease? I'm not so sure.

Aggressive i3 Regen

The Volt has two regenerative braking settings. With the shift lever in the normal D position, the regen is light, replicating the modest engine braking of a standard car with automatic transmission.

But drop the shifter into the L position, and the regen ramps up sharply, mimicking the stronger engine braking of a standard car in a lower gear. A big fan of stronger regen, I always drive my Volt in L.

The i3 has only one regen setting: Supersized. The i3 regen is stronger than any electric car I've driven, including the Model S. That makes for a very sporty feel that complements the car's overall character.

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

Interior

The i3 has a higher driver's position, more glass, and a more airy, open feel in the cockpit. The Volt, while equally comfortable, has a cozier, low-slung feel to it

Back seat room is limited in both cars.

With the driver's seat pushed all the way back (at 6 feet 2, that's where I set it), rear passengers in both cars will barely be able to shoehorn their feet and knees into position, with the i3 having perhaps an inch or two advantage.

With tall adults in front, it's virtually kids-only in back for both cars.

With the front seats in the mid-range of adjustment, both Volt and i3 have enough room for a pair of adult knees. Both cars are limited to two rear-seat passengers.

Rear headroom is about the same in both cars--just barely enough for a 6-2 guy like me.

Call it a toss-up of mediocrity for the folks in back.

Suicide doors

A noteworthy feature of the i3 is its rear-hinged back doors. (BMW understandably prefers the term "coach" doors to the more popular colloquial term "suicide doors.")

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

You either love 'em or hate 'em, and I happen to hate 'em. Rear passengers can't get out until the driver first opens the front door, thereby releasing the rear doors to be opened.

(It might be a good way to keep unruly kids inside, I suppose.)

On the other hand, with all doors open, the i3 is incredibly accessible. And it looks very cool.

2014 BMW i3 REx owned by Tom Moloughney

Cargo room

The Volt is the clear winner in this regard. The rear cargo area is about 15 percent bigger, and with rear seats folded down, the Volt will swallow a large mountain bike without removing the front wheel. I've carried all sorts of stuff back there; it's an amazingly useful space.

Because of the electric motor, REx engine, and gas tank underneath, the i3's rear cargo floor is several inches higher than the Volt's--one reason there's less total space.

But the i3 cargo opening is lower than the Volt's, at the same level as the floor. The Volt, on the other hand, has a deep lip over which cargo must be lifted.

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

Looks

The Volt has a pleasant, rather innocuous look to it, but the i3 shouts out, "Look at me! I'm different!"

Again, you either love it or hate it. And again, I'm not a fan of the car's appearance.

No accounting for taste.

Price

In my book, the Volt and i3 REx run neck and neck until you get to the sticker price.

Current Volt base price is $34,995, more than $11,000 cheaper than the i3 REx base sticker of $46,125.

Eleven grand will buy a whole lot of kilowatt-hours and gasoline to make up for the Volt's lower efficiency.

Using our previous cost-of-operation numbers, the payback period in electricity and gas savings for the i3's price premium works out to something like 200 years.

Which one to buy?

The Chevrolet Volt has a lot going for it. For many drivers, it virtually never burns gas. Yet it can go 300-plus miles, no sweat.

It has the second-highest owner approval rating ever measured by Consumer Reports (after the Tesla Model S). And it's $11,000 cheaper than the i3.

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

The BMW i3 is cutting edge, in both engineering and appearance. It's the most efficient car on the road. It drives like a BMW. And you never have to worry about range anxiety.

In the end, the decision-making process depends less on an exhaustive analysis of the two cars, and more on the buyer's driving profile and personal preferences.

To paraphrase George Costanza, "It's not the car, it's you."

Buy the Chevy Volt if:

Your typical day's driving is less than 40 miles. (Or less than 80 miles, if you have the option of plugging in at work.)

Your typical day's driving is more than 100 miles.

You take long cross-country trips.

Purchase price is a big factor.

You live in a mountainous region with long, fast uphill stretches of road.

You prefer a smooth, comfortable ride to a sporty, responsive one.

Buy the BMW i3 REx if:

Your typical daily driving distance is 40 to 100 miles (or 40 to150 miles if you can charge at work).

You want to drive the newest, coolest technology.

You take pleasure in driving the most efficient car on the road.

You put a premium on sporty, responsive handling and performance.

You like getting stared at on the road and constantly pestered with questions from strangers.

2014 BMW i3 REx range-extended electric car owned by Tom Moloughney - in dealership showroom

Bottom Line

These are two terrific cars. Pick the one that best matches your typical daily driving mission--and gets your juices flowing.

My counterpart Tom Moloughney came close to calling it a draw too, saying:

[The i3 REx] was indeed the better choice for me, but honestly, I would be very happy driving a Volt also, especially if I drove less than the 90 miles a day that I do now.

I don't think you can lose with either of these extended range electric vehicles.

Just pick the one that fits your budget, needs and desires and you'll be happy with whichever you choose.

Me? I'll go with the Volt. After three years, it's still the one.

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