"History," quipped America's greatest philosopher, "doesn't repeat itself...but it does rhyme." Mark Twain died 101 years ago, just as the practice of a whistle and a snap of the reins to your buggy's horse was giving way to hand-cranking newfangled automobiles.

I'm no Twain scholar, but it's easy to imagine him lowering one of those famous caterpillar eyebrows and raising the other as those nutty new contraptions clattered past his Connecticut home-rather like our contemporary bystanders in Newport Beach, California (though with much better eyebrow grooming), who stopped and pointed as we photographed a Prius test car next to our long-term Chevrolet Volt and Nissan Leaf. Those Twain-like glances are understandable, though; it's been a century since any of us has known anything but petroleum-burning propulsion.

What's brought us to this once-a-century inflection point? Pick your slogan: "Global warming is real!" "Imported oil endangers national security!" "Gas costs four bucks!" Whichever spikes their adrenaline level, people are starting to seriously ponder electric grid-assisted, or entirely grid-powered, automobiles (and creating some odd bedfellows along the way).

What are the tradeoffs with living with a plug-in car? To find out, we compared the Prius I mentioned -- which, at a 50 combined mpg, is the most efficient "conventional" car in the country (hands down, in fact) -- against these two levels of electro-pluggability. If you're curious to dip a toe in the electrical current (with the other remaining in a familiar barrel of oil), there's the Volt, which hedges its 35-40-mile EV bet with a range-extending, 1.4-liter engine. Want to swan dive into the EV deep end? The only reason a Leaf needs to visit a gas station is to put air in its tires.

And, yep, for the first time ever, we've enlisted a Prius as a mere technological yardstick. The flip side is the implication that it's time to finally admit that the Prius is actually a mainstream (and even profitable) car. Supporting evidence: The Prius recently cracked the millionth-U.S.-sold milestone; its once-bizarre drivetrain is now discussed in commodity terms; and its nickel-metal-hydride batteries (originally so fretted about) are trying to outlive the cars they're mounted in. It's "effectively" conventional, too, in the sense that if you're oblivious to what's going under the Prius' snout, it doesn't matter. Just fill 'er-up with gas like any other car. (No need to search for any of those "exotic" diesel stations, even.)

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MY BATTERY IS BIGGER THAN YOUR BATTERY

In the nearby diagrams of our trio's powertrains (simplified to their most basic principles), you'll recognize that the Volt plucks some crucial components from both the Prius and Leaf's toy boxes. Like the Prius, it has two sizeable electric motors connected via a planetary gear set; like the Leaf, it has is a very large lithium-ion battery. Ah, but it's how you stir the soup: Where the Prius' planetary system is basically a CVT that creatively blends in the engine's power (its smaller electric motor controls the mixing and sometimes acts as a generator), the Volt's planetary setup provides for a more efficient, two-step introduction of its electric motors' power. (The larger one operates at lower road speeds, and the smaller joins in at higher roads speeds to avoid inefficient overspeeding of the first.) And about those three clutches-hmm. Suffice it to say that by locking or releasing them in various combinations, the engine can spin the smaller electric motor (acting as a generator), and/or occasionally even directly couple to the mechanical drivetrain.

And why, you should be asking, does the Volt in gas mode deliver 13 fewer mpg than the Prius? Working against the Chevrolet's profoundly intelligent details are nearly 700 pounds of additional weight, greater frontal area, and the inherent inefficiency of repeatedly converting the gasoline's energy into different forms (electrical via the generator and chemical via the battery). Our guess is that this mileage number is going to improve bigtime in subsequent versions as the technology is refined. (The original Prius returned 41 mpg, remember.)

RANGE AND RECHARGING

This is where you're really smacked in the face with how different the Leaf, Volt, and Prius truly are. The Leaf is like a frisky puppy on a short leash-with a choke collar latched to it. When the Nissan's mammoth battery stops, it's flatbed time. Fortunately, you're repeatedly warned as the apocalypse approaches, via voiceand warning-light admonitions, with the car eventually lapsing into a slow speed "turtle mode" to embarrass you into finally pulling over. We intentionally depleted our Leaf to experience what it's like, and it proved to be a puzzling non-event. While in turtle mode, I happened to stop at a crosswalk, and when I put my foot down again-nothing. The car had lapsed into a coma. Four of us pushed it back to our garage's 208-volt charger where it hungrily absorbed 25.1 kW-hrs of electrical energy. (How's that possible with a "24 kW-hr" battery? Charging inefficiency.) In spectacular contrast, it's a strain to even notice the Volt's transition from EV to extended-range mode; your best clue is the subtle swapping of the battery-level and fuel-level icons on the digital display.

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More plaudits go to the credibility of the Volt's EV range estimation. Unless you drive like a maniac, if the Volt's display says it'll go 37 miles in EV mode, it'll deliver between 36 and 38. By comparison, the Leaf's is virtually an info-slinky. Pull away from the charger with an indicated 106-mile range, and it'll drop eight miles by the end of the block. I found myself finally ignoring the numbers and counting the remaining battery bar-graph segments, but even this is iffy as, per Mike Duoba of Argonne National Lab, "a battery is like a rubber bucket." Depending on the circumstances, sometimes there's more in the stretchy bucket, sometimes less, though either instance counts as a "full" battery. I tended to drive in a consistent manner and came to expect 75 miles as my practical range. Fortunately, Nissan's Carwings intelligent information system can guide you to the nearest charger it's aware of (though when I wandered into a nearby Nissan dealership-with three chargers prominently displayed in front-chaos reigned: "You're the first guy with a Leaf who's come in here! Hey, Bob, what do we do now?") Instead, we quickly got to know our local, independent ChargePoint stations, part of a slick network cropping up in shopping malls and the like. (Cool details? If a prankster unplugs your car while you're malling, Charge Point will send you an email alert.)

In the graph on page 104, you can get an idea of what your life with these cars is like. The Prius takes about two minutes to fill up with gas, and-assuming for comparison's sake, you drive the generally acknowledged 15,000 miles per year-you might go nearly two weeks before you need to stop again. The Volt's battery had to nurse on our 208-volt charger for about four hours to "fill up;" the Leaf demanded 7.5 hours for twice the range at the same speed. It's plausible (but not recommended) to regularly charge the Volt with household current (around 10 hours), but almost mathematically impossible with the Leaf (over 20 hours).

A consequence of the Volt's 35-mile EV range (it sometimes tickles 40, but a lot less in colder climes) is that, to complete that daily 41 miles (15,000/365), the engine is needed for 6 miles of it. The upshot is that, despite its teensy 9.3-gallon tank, the Volt can go ages between refillings (our last fill-up spanned 1118 miles).

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THE SOUNDS OF SILENCE

As we walked into the house after a day of cruising around in the Leaf, my wife said, "I've got to lie down, my ears are ringing." Daughter Catherine said, "Me, too," and went over to the piano and struck a very high key. "Pinggg"-yep, that was just about what I was still hearing as well. Fortunately, I've got a sound meter.

The nearby images are spectrographs of our trio as they moderately accelerated to 50 mph, cruised there briefly, and braked to halt. For those of you who don't look at spectrographs every day, it's sound visually pulled apart. The red colors mean intense sound energy; blue, much less. Time is passing left to right, and frequency rises as you go up. You see what I see?

The Prius is comparatively noisy (lots of red, particularly while accelerating). The engine fires up after just a few feet, and its noise-generated through a wide spread of frequencies-rises together with speed. (Incidentally, those occasional vertical lines are simply bumps being registered). Once it's at 50 mph, its planetary CVT lets the 1.8-liter's revs-and noise level-precipitously drop.

By comparison, the Volt in EV mode is much, much quieter, but note those faint, arching lines while accelerating? They're the telltale acoustic signature of an electric motor; the rest of it is an assortment of road and aerodynamic noises-virtually what you'd find if the car were being towed by a rope. To the human ear (instead of a microphone), the Volt's electric motor whine is briefly detectable as you pull away from a stop. However, in the Leaf's case, those arching lines are strikingly more intense and persist up to much higher speeds. And these are precisely the culprits we were hearing that day (and for a while after we stopped driving).

So is this a real or imagined problem? Among the several staffers who drove the Leaf, only myself and another editor were bothered by these high-frequency sounds. I gave my pal, Paul Van Valkenburg (author of a book on tinnitus), a ride in the Leaf and, although his perception of high frequencies has diminished (this happens with age; mine's almost as bad), he noted that it doesn't take a very big dose of it to affect you.

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The irony is that the Leaf is actually a very quiet car. Nissan has done an A+, five-star, Rolls-Royce-ian job of stifling the wind hiss, tire roar, and road boom that plagued so many early electric vehicles. How curious.

NOT A NATIONAL SOLUTION

While electric cars are the darlings of coastal California, they emphatically don't make sense to blindly deploy everywhere. The amount of CO2 emitted by power stations varies wildly across the nation, ranging from a scant 0.002 lb/kW-hr in Vermont (which employs significant nuclear generation) to 2.14 lb in Wyoming (lots of coal).

The CO2 cart can quickly tip against EVs, though it's certainly another matter if your priority is domestically produced energy, for instance.

Consider our graphs: In many states, not only can the Prius leave a smaller CO2 footprint than the electric Leaf, but the Volt would be responsible for less CO2 were it never recharged in the very state in which it's built. (None of our CO2 numbers, by the way, includes the emissions owed to producing and transporting gasoline to stations, or, similarly, the fuels delivered to electrical powerplants.)

So how long do these new batteries last? While the Prius' nickel-metal-hydride packs have proven to be indestructible, the situation's not so confident with this debut crop of lithium manganese chemistries. Besides Tesla, which has far and away the most real-world data with its small liquid-cooled cells (an accumulated 11 million miles from 1600 Roadsters) every manufacturer in the game has been frantically running accelerated testing to figure out what's going to happen.

And according to Darryl Siry's observation in Wired, there's a crucial difference between the Leaf and Volt batteries that bears careful watching. Nissan is betting on a fan to equalize its internal temperatures; heat buildup is dissipated by simple air cooling. Quite differently, heat within the Volt's LG Chem battery is managed by space-consuming, but more conservative, liquid cooling. Moreover, the Volt cycles throughout a delicate 50 percent of its capacity. The Leaf? More than 80 percent. Nissan, one concludes, is being very confident here. Fortunately, both batteries are warrantied for 8 years and 100,000 miles (not including normal degradation, which GM calls between 10 to 30 percent; if it fails, you'll get a replacement that's appropriately degraded).

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The even bigger question to chew on is these batteries' spectacular cost. At the minimum $500 per kW-hr they're presently figured to cost (up to $625 as an assembled battery), the Volt's 16 kW-hr pack rings in between about $8000 and $10,000, the Nissan's at an eye-watering $12,000-$15,000 alone, a sizable chunk of the Prius' base price. Thank heavens that both the Volt and Leaf qualify for a federal $7500 tax credit, with our Leaf eligible for an additional $5000 in California. The 2013 model year Volts may be eligible for the same when it's is submitted to the California Air Resources Board as an Advanced Technology Partial Zero Emissions Vehicle.

Combining these credits brings our Leaf's base price down to $22,070, at which you're almost a fool not to buy it. And for you Thomas Paines out there flinching at this egregious government interventionism, would you be happier sending the petrodollars they'd otherwise consume here to overseas oil producers?

WATTS BEST FOR YOU?

We've spent some time hopscotching between some of the issues orbiting plug-in vehicles, but which of these three actual cars should you consider parking in your driveway? Go stare at yourself in the bathroom mirror. Close your eyes tight, open them suddenly and tell me who you are.

Live in an apartment? Reside in one of those red-colored, high CO2 lb/kW-hr, states? Is your life already stressed out and full of yellow sticky notes with to-do lists scribbled on both sides that you're sure you put in your pocket but aren't there now? Listen. The Prius is the affordable, low-blood-pressure, push-button pick to simultaneously thumb your nose at OPEC, give the polar bears a break, save some cash at the pump, and get on with your heart-attack life. Driven back-to-back with the other two, its road noise seems surprisingly hectic (ironic, given that it has a regularly running engine to mask much of it). And we wonder if the car's ride and handling hasn't been made intentionally weird as a personality trait. Magically, it simultaneously wallows over road undulations and pitter-pats over individual bumps.

Moreover, it handles almost as if it were French (not a compliment). But the Prius delivers take-it-to the-bank surrealistic mileage, a proven track record, and none of that plug-in funny business. And if its flash-forward styling doesn't antagonize you, here are the keys.

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Say you own a home in an EV-friendly state, your default cable channel is Current TV, you count the days to Steve Jobs' latest i-anything, predictably drive no more than 60 miles a day, already own a Prius, and think additional daily chores will bring a more satisfying routine to your life. Besides the fact you should have been reading this in our iPad edition, you are Leaf material, my friend. You've somehow made it through a micro-mesh filter to slip behind the wheel of what's truly a historic automobile. It rides a little heavily, perhaps; as noted. I personally don't care for that whine it makes, rear passengers' toes don't go very far beneath the front seats, and it handles like a bowl of cream of wheat. But it's astonishingly well executed and, oh, those moments when it vacuums ahead as if you were a canister in one of those pneumatic mail tubes -- whoosh -- they're magic. One day I was a carpool driver for some kids in a children's theater group. As I dropped them off one by one, I watched as they strolled away, never aware they'd just ridden in their first electric car. The Leaf is that good.

The rest of you still staring in the mirror should say hello to the Volt.

And I see your eyebrows are canted at that very Twain-like angle. "What? Me?" you mumble. Yes, you. And me, too. The Volt has two drivetrains because the likes of us need two drivetrains. We'd forget to plug a Leaf in sometimes and end up riding the bus to work the next day. Stuff happens, plans change. We would also rather spend the price premium the Volt demands entirely on the Volt, instead of a Leaf and that second, long-range car we're going to need.

Furthermore, you get to drive the automobile with the single most sophisticated powertrain on the planet, period. That's a savory contemplation many will agree is worth overlooking the car's pedestrian-grade interior materials, its four instead of five seats, difficult forward vision (gigantic A-pillars), finicky touch-sensitive buttons on the center console, heavy-feeling ride, and squishy brake-pedal step-in. The Volt drives like a regular car -- instead of the historic inflection point in personal transportation it really is.

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