At Tom and Marcia Lewis' house in Annapolis, the future meets the past.

Last year the couple installed solar panels on the roof of their 110-year-old frame house in the city's Historic District.

"We're very much in favor of alternative energy sources," Marcia Lewis says.

Residential solar energy sales are booming in the United States, and property owners are increasingly finding ways to combine historic preservation with energy preservation.

The Lewises had their panels installed on the back roof of their three-story home on Conduit Street. From the front, the house still looks like a "classic Victorian," Tom Lewis says.

But the couple's electric bill has decreased by about a third. "It was a nice win-win," Tom Lewis says.

In Howard County, Lawrence Cheskin and his wife, Lisa Davis, installed solar panels behind Burleigh Manor, a 200-year-old Federal-style home.

"It was a bit of a struggle because of the nature of the property," Cheskin says.

While Cheskin was enthusiastic about pursuing alternative energy sources, his wife wanted to maintain the historic character of their home.

"I knew when I was looking for ways to be eco-friendly, she was not going to be happy with an ugly solar panel perched on the roof," he says.

"I was more skeptical about the aesthetic of it," Davis concedes.

They considered putting the panels on outbuildings but ultimately placed them in a field behind their house. "They are making a huge difference in the bill," Cheskin says. "The meter runs backward when the sun is out."

The couple expects to recoup the $30,000 outlay for the panels in about 20 years. "We're trying to do what we can to get off the grid," Davis says. The biggest problem, she says, has been keeping the family's ponies out of the enclosed area where the panels are located.

Although solar energy can be a boon to homeowners, installing the panels on historic properties or in historic districts still is not common, and it is not without controversy.

National Trust for Historic Preservation guidelines recommend placing panels out of sight and caution against damaging roofs, dormers, chimneys or other features of a historic home.

Jurisdictions in the Baltimore area have adopted similar guidelines when reviewing requests from property owners.

"We've always supported solar installations; it's a matter of where they are installed," says Kathleen Kotarba, director of Baltimore's Commission for Historical and Architectural Preservation. Its guidelines, developed in 1980, call for putting panels in as inconspicuous location as possible, she says.

The Annapolis Historic Preservation Commission takes the same approach, although in Annapolis, the homeowner must not only consider views from the street but also from the city's waterways, says Lisa Craig, the city's chief of historic preservation.

"If someone wants to place solar panels on a building and it's not in the public view ... then we work with the applicant so they are not damaging a significant amount of a historic roof," she says.

In the past three years, only six homeowners have applied to the city's Historic Preservation Commission for permission to erect solar panels, and three were approved, Craig says.

"It's reviewed on a case-by-case basis," she says. In some cases, the property owners decided not to put up the solar panels because of the expense or because they didn't want to detract from their historic properties.

Often energy audits will uncover more effective or less costly ways to save energy, such as improving insulation and weatherstripping, she says.

Karin Brown, chief of preservation services in Baltimore County, says the county's Landmarks Preservation Commission has approved solar panels on only two properties.

She says one reason homeowners are leery about installing green technologies is they fear losing tax credits that come with owning historic homes. A property owner can lose those credits if the historic nature of the home is damaged.

The Rodgers Forge Homeowners Association is weighing this question now as it considers a request for solar panels from one resident. A committee studying the issue made its first report to the association board in early January.

"What they're moving toward recommending to the board would be a set of guidelines that would allow solar panel installations in Rodgers Forge if certain thresholds and criteria about the placement and design could be met," says association President Stu Sirota.

State law prohibits homeowners associations from putting undue restrictions on property owners who want to use green technologies, except in cases where the homes are on the Maryland Register of Historic Places or the National Register of Historic Places.

Rodgers Forge is on the Maryland Register, Sirota says, so the association must consider whether property owners might lose tax credits if solar panels are installed in the district.

"There are many cases around the country where we see solar panels have been done," Sirota says. "It seems, looking at other examples, it can be done."

Balancing environmental preservation and historic preservation can be complicated, says Charles Wagandt, president of the Oella Co. He has spent 40 years restoring the former mill town in western Baltimore County.

"It's a tough question," he says. The owner of one new home within the Oella Historic District installed solar panels, but Wagandt says putting the panels on a historic home is another matter.

"We would not allow panels on a historic property that would be visible," he says. "I think the solar panel on a historic home looks like hell."

Solar panels are but one of a number of continuing battles with homeowners who are trying to fight energy costs. A more common problem is homeowners who want to install replacement windows that don't meet the district's architectural guidelines, he says.

"Some of the people here believe they are stewards of a historic home," Wagandt says. "They want to turn it over to subsequent stewards. A considerable number feel that way, but some don't."

Solar panel guidelines

Here are some guidelines for solar panel use from the National Trust for Historic Preservation:

•Place solar panels on the ground in an inconspicuous place, if possible.

•Put panels on new buildings or additions, if possible.

•Place panels flush with, or no more than a few inches above, an existing roof. On a flat roof, set the panels back from the edge.

•Ensure the panels and its supports blend into the surrounding features.

•Don't place panels on street-facing walls or roofs.

•Don't alter roof lines or dormers.

•Don't damage the structure. Install solar panels so they can be removed without damaging the historic structure.