The Volt is more flexible. It gets 25 to 50 miles on a single electric charge before a gasoline-powered generator provides electricity to power the wheels for an additional 300 miles.

When it comes to the infrastructure to recharge vehicles, Omotoso said: "We have 160,000 gas stations across the country, but there are fewer than 1,000 public charging stations."

Still, range anxiety might be slightly overblown. At least that is Nissan's argument.

Nissan said U.S. census data show that 95 percent of Americans drive fewer than 100 miles a day and 75 percent drive fewer than 40 miles daily. Sixty-three percent of those who responded to the Consumer Reports survey said they traveled fewer than 40 miles a day.

When it comes to cost, of the handful of electric vehicles for sale, one is the $100,000 Tesla Roadster; another is the $41,000 Volt, "a small car that is priced like a Cadillac CTS," Omotoso said. It makes the $33,630 Leaf seem highly affordable.

A maximum $7,500 federal tax credit helps bring costs down, and there is talk about turning it into a rebate that consumers get immediately at purchase instead of waiting until tax time. Incentives are scheduled to end after the first 200,000 electric vehicles are sold, but proposals to increase that to 500,000 vehicles are out there.

Keep in mind that changes are taking place in gasoline engine and transmission technology, which are improving fuel economy at a much lower cost than electric vehicles, Omotoso said.

Given all the market uncertainty, how realistic is meeting the goal of 1 million green vehicles by 2015?

J.D. Power's forecast is that we'll get to 700,000 or 750,000 — short of the target but still significant, Omotoso said.

The Indiana University study said it is unlikely, given automakers' current production plans.

But the panel thought it could happen within a few years after that.