Would You Buy an Electric Car?

President Obama revealed what he might think we should be driving when he visited Tesla Motors  , a firm building electric cars in San Carlos, California, while on his Tonight Show trip to the Coast.

Unlike political rhetoric read from a teleprompter, cars are real. You can touch them and drive them and determine whether or not they're good, bad or indifferent. And the reality is that electric cars don't match the performance of conventional vehicles you're driving now.

There's one major shortcoming, which manufacturers never seem to cover in detail, illuminated in a  March  26 Silicon Valley Mercury News driving review.

Reporter Matt Nauman spent an afternoon "thrashing" a Telsa Roadster on the two-lane roads in the hills behind Palo Alto, California. The Roadster is based on the excellent Lotus Elise  bonded aluminum chassis. The two-seater has an electric motor powered by 6831 lithium ion cells.

Initial performance is impressive, according to Tesla, with 3.9 second 0-60 times and top speed is 125 mph, but it's a little pricey at $109,000. Fast when fully charged.

But how far can you drive on a charge?

According to Nauman, repeating the company's claims "... you can drive nearly 250 miles between charges." But when he elaborates, his own experience is different.

"In all, I spent more than three hours behind the wheel, logging about 100 miles," he writes. That calculates to about a 30 mph average. Hardly a "thrashing." Sounds more like more like stop-and-go driving.

He continues, "When I handed the keys back. . . .the range estimator said it had enough juice left for about 80 more miles." So his driving range, had he continued, was about 180 miles, yet the manufacturer claims a 250 mile range. That's a big your-mileage-may-vary discrepancy.

Tesla also plans introducing their four-door Model S sedan. The 4000 pound car will have a 160-mile battery pack standard, with 230 and 300-mile packs optional. Once again, there's no explanation of how driving conditions might affect these mileages. So the question is: could you, you wife and child, plus luggage, load up and drive 286 miles from Los Angles to Las Vegas on a single charge? And can the Model S maintain the typical  80 mph cruise on I-15 that distance?

What no one mentions is that as batteries discharge through current flow to the electric motor, they deliver less power. Consider leaving your car lights on. Over time, the lights dim because the battery can't maintain the current flow for normal brightness. So the lights dim and then go out. They don't stay bright, then go dark as if the switch were turned off.

So with a full charge, the Roadster may do a 3.9 second 0-60, but near the end of its range limit, a 0-60 test would take much longer. You would also notice the power decline in passing and going up hills.

My family recently took a road trip in our humble Ford Focus station wagon. We covered 306 miles on one tank and averaged 30 mpg. Plus, with traffic flow, we never saw under 60 and typically cruised at 75-80 on the interstates.

Now, the question is, why would I want to buy an electric car that can't match the performance of a humble econobox?

I'm still waiting to read a full instrumented Telsa road test. And what I would like to know is how far will a Roadster go on a single charge averaging 80 mph on an interstate, up hill and down.

Like President Obama's campaign promises, my guess is that driving reality will greatly differ from the rhetoric.

Ironically, I emailed Mr. Nauman a couple of questions about his driving review. I received an automated response that the first week of April would be his last at the paper. He might have accepted a government job or maybe the Mercury News is laying off staff. Either way, it seems an ominous sign for the market viability of the Tesla.