WASHINGTON – Regulators and environmentalists here say criticism of slow sales for the newly introduced Chevrolet Volt and Nissan Leaf electrified vehicles is off base and the cars must be given more time to gain traction in the market.

“It is way too early to judge success or failure,” Ron Medford, deputy administrator of the National Highway Traffic Safety Admin., says on the sidelines of the Washington Auto Show.

The Leaf and Volt particularly have been criticized as unpopular because of their low sales volumes. Nissan and General Motors both blame limited supply of the cars and consumers’ unwillingness to leap into radical new technology.

The Leaf runs on electricity for some 90 miles (145 km) before it needs a recharge. The Volt will travel about 40 miles (64 km) on electricity alone, after which a small gasoline-powered motor/generator takes over to send it another 300 miles (483 km) before the driver must recharge or fill up.

The cars are expensive for their respective segments, also leading to reluctance among shoppers.

The Leaf accounted for 9,674 deliveries last year, according to WardsAuto data, while the Volt drew 7,761 buyers. Both totals fell short of company expectations. For perspective, the Chevy Cruze compact car sold more than 230,000 units last year.

Market acceptance for new technologies in the U.S. historically has been slow.

The Toyota Prius, for example, sold 5,562 units after it was introduced in 2000, WardsAuto data shows, jumping to 15,500 sales in 2001 and 158,884 in 2007, before the market tanked.

So to characterize the Volt and Leaf as flops would be wrong, Washington insiders say. Both figure into the auto industry’s ability to reach strict new corporate average fuel economy and emissions-reduction goals starting with the ’12 model year.

“I think it is insane to judge the (EV) market by one year of sales,” says Roland Hwang, director-transportation program at the National Resource Defense Council, a Washington lobbyist for environmentalists.

“The Volt and the Leaf are fantastic vehicles. The fact that they sold on order of 15,000 vehicles in the first year is a fantastic story.”

Mitch Bainwol, CEO of the Alliance of Automobile Manufacturers, wants the cars’ success judged after five years in the market. But the federal government needs to double down on the technology gamble, as well, by offering meaningful consumer incentives and speeding up the infrastructure such vehicles demand.

“The feds need to step up too,” he says.

Electrified vehicles took more flak earlier this week, when GM Chairman and CEO Dan Akerson testified before a U.S. House committee on the safety of the Volt.

Federal regulators were able to spark a fire in the Volt’s battery pack during testing earlier this year. GM strengthened the battery pack and the NHTSA cleared it of safety concerns. But legislators wanted to know if either were slow to release information about the fires.

Akerson told lawmakers the car had become a “political punching bag.”

Margo Oge, director-Office of Transportation and Air Quality at the Environmental Protection Agency, who also is a Volt owner, agrees with Akerson. “It was very unfortunate,” she tells WardsAuto.