Thanks to the Department of Energy, a lot more residents of the Germantown area are driving down I-270 to work in Washington these days.

Not that the DOE wants it that way. But its decision to cut off bus service to its headquarters at the Forrestal building has forced perhaps hundreds of non-DOE people to climb back in their cars for the daily commute downtown.

When the new department was founded more than two years ago, a shuttle bus service was inauguarated to transfer employes at the Energy Research and Development Administration in Germantown to the Forrestal Building for official purposes only, such as meetings with the brass.

Instead of using minivans or minibuses as many federal agencies do, DOE contracted with the private Gold Line bus company for 46-seat buses to make 10 runs each way daily, beginning at 6:30 a.m.

When it soon became clear that roughly only one-third of DOE's Germantown employes occupied the buses at any given time, the express service to Forrestal was opened up to non-DOE passengers at 75 cents a ride.

It was a bonanza for Germantown area residents who worked in the many federal agencies near the Forrestal Bilding. And it was a great convenience for those who wanted to go downtown during nonrush hours when the buses were nearly empty.

Then, on April 1, the DOE cancelled the express service, switching to 14-passenger minivans for financial savings and citing federal regulations against the practice.

A DOE spokesman explained that the General Accounting Office has ruled the government is not in the business of providing commuters with transportation and vehicles are to be used for official purposes only. There also was concern about insurance coverage for non-DOE riders in the event of an accident, he added.

Metro buses do not go out as far as Germantown. A private bus service that leaves from nearby Montgomery Village goes to Metro Center downtown, far from the offices of many federal agencies. The last bus for Montgomery Village leaves at 5:47 p.m., too early for some government employes.

The nearest subway stop, at Shady Grove, is not expected to open until 1984. The train from Germantown arrives at Union Station, a good half-hour hike from the federal office buildings in Southwest.

For Dan Inamorato, a DOE photographer who lives in Montgomery Village, the discontinuance of the DOE express bus system has meant an extra hour on his daily commute and $20 more a month for transportation.

"It was just a 10-minute drive to get to where the Germantown bus left from my home," Inamorato said. "Now I take a train to Union Station and walk across town for 30 minutes. I could take the Metro but it takes as long if there are tie-ups.

"And I have to carry about 45 pounds of heavy camera equipment so walking across the Mall isn't a thrill."

Still others switched back to their cars and sought companions with similar work schedules for pools.

Inamorato and others sharing his plight have gotten together a few times to discuss forming a commuters' association that could lease buses to replace the DOE system.

After they reviewed bids from bus companies, they figured the group could offer an arrangement that worked out to $4 a day round-trip.

"That wasn't too bad since parking is about $4 a day here anyway," Inamorato said. But the plan fizzled when too few potential riders were willing to commit themselves financially to starting the services.

They will try again, Inamorato said.

Meanwhile, John Matthias, the Germantown coordinator for the Maryland-National Capital Park and Planning Commission, said the county plans to expand the parking facilitites at the Germantown and Metropolitan Grove train stations to encourage rail transit.

The county also plans within the next few months to extend its intracounty bus service to Germantown in the rush hours and will make a greater effort to help coordinate van and car pools, Matthias said.