Employees at General Motors' plant in White Marsh, Md., have an unusual workplace benefit: Anyone who drives an electric car can plug it in to charge while they work.

At the plant, which produces transmissions and electric motors, workers can park their electric vehicles — or EVs — in any of eight spaces under two solar-powered canopies in the employee lot.

It's not surprising that an automaker that makes plug-in electric vehicles is emerging as a leader in working to expand charging stations for consumers. But now other large employers are joining efforts to boost workplace EV charging, including Verizon, Google, 3M, General Electric and Eli Lilly & Co.

"We've got industry acknowledging that this is a mode of transportation for the future, and they're taking action to start to lay the groundwork," said Jill Sorensen, executive director of the Baltimore-Washington Electric Vehicle Initiative, a five-year-old nonprofit.

Plug-in electric vehicles have been on the market only a couple of years, including all-electric models such as the Nissan Leaf and hybrids, which have small gas engines, such as the Chevrolet Volt. But last year, EV sales tripled, with Americans buying more than 50,000 electric cars.

In the meantime, public charging stations have been cropping up — about 5,000 are available nationwide, the U.S. Department of Energy said. They can be found at mass transit stations, universities, public garages and retailers such as Target and Walgreens.