They've been touted as the green future of transportation. Billions have been invested to bring them into being, by companies big and small and governments around the world. Rules have been rewritten, infrastructure reconsidered, lofty promises made.

Indeed, the powers that shape the cars that you and I drive are doing all they can to bring an electrified automotive future into being. There's just one big question that hasn't been answered, and on this Earth Day weekend it's worth pondering:

Will there be buyers for all of these electric cars?

So far, the answer isn't promising.

Why electric cars haven't taken off
Proponents of electric cars like to say that the adoption curve so far looks like that of hybrids in the 1990s. That's true enough, but whether the technology will continue on that path -- whether it'll make the leap from gadget-geek novelty to the mass market, as hybrids have -- is still very much an open question. And there are real reasons to be skeptical.

The secret to the success of hybrid cars, after all, was that they didn't require anything new and different from their drivers. For the most part, living with a hybrid is like living with any other car: You drive it the same way, with the same controls; you put gas in it at any gas station when the tank runs low; you take it for an oil change every now and then and have the dealer check it over once every year or so. Nothing about the hybrid-ness of it requires a major change in consumer behavior -- or in consumers' expectations.

That's not true of electric cars. At least at the moment, purely electric cars come with what General Motors (NYSE: GM) has cutely termed "range anxiety": How far will you be able to go, and where will you be able to recharge? GM "solved" that problem by including a gas-fueled onboard generator with its Chevy Volt, but that functionally makes the Volt just another hybrid, albeit an innovative one.

Meanwhile, with pure electric cars like Nissan's (OTC: NSANY.PK) Leaf, range remains a big concern for potential buyers. While Tesla Motors (Nasdaq: TSLA) has managed to build cars with range comparable to gas-fueled vehicles -- albeit at a steep price -- none of the other electrics available, including the Leaf, can go much more than 100 miles without a charge.

And that's under optimal conditions. As it turns out, the range of an electric car is dependent on considerations that don't come into play with gasoline, like your driving habits, and the weather. A car that will comfortably go 100 miles when driven carefully on a warm, dry day might go only 70 on a cold day when you're in a hurry. If your office is 40 miles from home, that's a problem.

Of course, the range problem is one that will be addressed in time, as batteries continue to improve and automakers (and drivers) gain more experience with the technology. The more difficult problem lies in the infrastructure: Where do you recharge when you're not at home?

That question is a little harder to answer.

A slow-growing market, with a more viable alternative
The easy answer is that charging stations will become more common as electric cars become more common, but that's a chicken-and-egg problem. Meanwhile, while electric cars seem to be talked about just about everywhere, there aren't actually very many on the roads.

Just over 17,000 electric vehicles were sold in the U.S. last year, which sounds like a lot -- but that's less than one-tenth of 1% of the total market, about equal to the number of F-series pickups that Ford (NYSE: F) sells every 10 days or so. That number is sure to go up this year, assuming Tesla gets its Model S sedan into production this summer as scheduled, but where does it go from there?

Tesla has more than 8,000 reservations, complete with deposits, for the Model S -- enough to account for this year's planned production and then some. But Tesla has a cool factor, and a following among well-heeled gadget geeks. Those fans are likely to keep the company's production lines busy for a few years, but will the company be able to build its appeal beyond there?

That's yet to be determined. So the question is whether Ford will be able to sell more than a handful of copies of its new all-electric Focus. Since its launch in December, the company's sales have been unimpressive: Only about two dozen were sold through March.

The likely future for electric-car technology
Ford CEO Alan Mulally seems untroubled by the low sales of the Focus Electric and emphasizes that the company's electric-car vision is a "long-term journey." But like rival Toyota (NYSE: TM), Ford is hedging its bets on electric cars by investing heavily in more-advanced hybrids, like the upcoming new "plug-in" hybrid Fusion sedan. Ford expects hybrids and electrics together to account for up to 25% of its sales by 2020 -- but it also expects that hybrids will make up most of that figure.

Toyota's chief engineer recently expressed a similar view. While Toyota will continue to keep its technological options open, it's clear that ever-more-advanced hybrids will be its priority for the time being.

And that's probably how this will play out, at least over the next decade. Electric cars seem to hold so much promise, but the compromises they require have turned out to be a hard sell in the mass market. It still seems likely that the promise will be tapped eventually, but the safer bet seems to be on hybrids -- at least for the foreseeable future.

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