Eldorado, N.M. ? It’s sizzling outside in the desert heat, yet Fred and Barbara Raznick are nice and cool inside their solar-powered adobe home without air conditioning or ceiling fans.

The south side of the home is covered with windows that let sunlight in during the winter and keep it out in the summer.

Barbara and Fred Raznick stand in a back door of their passive solar home in Eldorado, N.M. Floor-to-ceiling windows along the south side of the home allow sunlight inside the 22-foot-wide home in the winter, while keeping it out in the summer.

“You kind of feel like the house takes care of you,” Fred Raznick said.

According to the 2000 Census, this community of 5,700 people near Santa Fe has the nation’s highest percentage of homes heated mainly by solar power: 13.2 percent. Two Hawaiian villages rank second and third.

The communities appear to be remnants of a stalled movement with its roots in the 1970s. According to the census, the number of U.S. homes heated primarily by solar energy fell from 54,536 in 1990 to 47,069 a decade later.

Federal and many state tax credits for solar homes have long since dried up, and some suggest that poorly designed homes have hurt solar power’s reputation. The movement also has been hurt by the growing availability of natural gas.

In New Mexico, with its often cloudless winter sky, hundreds of solar homes have been built in and around Santa Fe, Albuquerque, Los Alamos and Taos, where KTAO calls itself the only solar-powered radio station on the planet.

In the ’70s, a billboard at the entrance to Eldorado touted the new development as a solar community, attracting idealists who wanted to put solar power into practice and families looking for affordable housing.

Homes were oriented toward the south to take advantage of the sun, which shines about 75 percent of daylight hours in New Mexico, where Santa Fe-area temperatures range from 20 degrees in the winter to the 90s in the summer. Many homeowners built the north sides of their houses into the juniper-dotted hillsides for better insulation.

New Mexico’s solar push in the ’70s was also aided by technical help from Los Alamos National Laboratory. Solar builders were able to tell homeowners how much money they could save with solar or predict what would happen if, for example, windows were moved or curtains added.

“We weren’t just shooting in the dark, but this was a new methodology behind us,” said Mark Chalom, a Santa Fe architect who designs solar homes.

By the 1990s, however, Eldorado’s billboard had come down and solar-home construction slowed to a trickle. “The natural gas line came out and that was the end of it all,” Chalom said.

Some solar homes have been built in recent years, but in nowhere near the numbers seen in the ’70s. As of 2000, Eldorado had 317 solar homes.

Solar homes are active or passive or both. The Raznicks heat their home with a passive solar system, which does not use pumps or fans to move hot air or hot water around the house. Their water is heated by an active system that uses solar panels on the roof.

Sunshine heats the tile floors and interior walls, including waist-high heat-absorbing masonry walls about a foot from the windows. The interior surfaces radiate the heat, much like a sidewalk on a summer evening, and the 2-feet-thick walls provide enough insulation to keep the home warm or cool.

“I love it in the winter,” said Raznick, a property broker. “The only time we really turn our heat on is in the bathrooms in the morning if I get up before the sun comes up and there’s a chill in the house.”

The cost for solar heating, electrical and water heating systems varies widely based on location, the home’s size and types of appliances. Experts say a well-designed passive solar home provides 75 percent to 80 percent of all heating.