The sky was heavy and gray. The air was a misty drizzle interrupted by heavy downpours. It was the perfect day to promote solar energy.

The unveiling yesterday of 18 solar-powered homes built by college students on the Mall was not marred by the persistent rain showers. Optimistic, java-fueled students, who had been assembling the homes in Washington for the past week, were ready for the weather.

"We're, like, second behind Seattle in overcast days, so we need to be able to function well on days like this," said Rosemary Lapka, 21, one of the Pittsburgh students who helped design an angular home that resembled a Scandinavian ski lodge.

They are competing in the second Solar Decathlon, a competition in which student engineers, interior designers, architects, designers and others create a small home completely powered by the sun. They must be able to cook meals, run hot water and power an electric car.

"We've got to cook five dinners next week. Including one for a bunch of reporters, so I hope that one is good," said Najahyia Chinchilla, 27, a graduate architecture student at the University of Maryland.

Planning began two years ago, and construction on the Mall started Sept. 29, when buzz saws hummed and drills buzzed until Solar Village, complete with sign posts, mailboxes and potted mums, rose from the strip of land between the Capitol and the Washington Monument.

Some homes were carted here nearly whole; others were assembled largely on the Mall. They come from as far as Madrid or as close as College Park.

"We built this on a steel chassis, so we just trucked it right over," said Matthew Wagner, 24, a Virginia Tech graduate architecture student. "The house did 70 mph on the way over here. So we figured we already proved it can take some pretty good wind."

Some houses reflect their origins. The Florida International University entry is a glass U-shape, decorated with sea grass and tangerine-colored furniture.

"We let the outside in. We created something that looks like a Florida courtyard, something that can be one, big entertaining area," said Robert Perez, 30, a graduate architecture student from Miami.

The house from the New York Institute of Technology looked like a futuristic Manhattan loft and came with a fast-talking PR woman.

The living area has deep cardboard recliners, crushed sunflower hull tables and personal air conditioning tubes to "create micro-atmospheres," said the spokeswoman, communications student Shana Lerner, 25.

The countertops made of recycled newspapers impressed Bob Shaw, 63, who traveled from Detroit for the event.

"We've been looking at this for a long time; we want to build a house of our own using some of these elements," he said.

He wanted to see the solar panels, hydrogen cell systems and structural insulation panels. His wife, JoAnn, 68, was looking at the aesthetics.

"I want to know it's comfortable, livable. This one is nice," she said of the University of Maryland entry.

It was impeccably designed, right down to a closet full of Terrapin clothes, modern furniture and the LaRousse Gastronomique cookbook displayed in the kitchen. All the lights were on, someone was Googling on a computer, a ceiling fan was spinning overhead and a tourist flopped on the couch and flipped through news channels on the flat screen television.

Their 51 solar panels were drawing 17,500 watts to power the buzzing house, even through the cloud cover.

Engineering is historically the university's strong suit. In the 2002 decathlon, the team created a house that took fourth place in a competition scored in 10 categories.

"The engineers scored pretty low in the, um, livability department," Chinchilla said. "So we learned and made it a little nicer this time."

The homes will be open until Oct. 16. They are judged daily, and the winner is scheduled to be announced Oct. 14.

The team from the University of Missouri at Rolla and Rolla Technical Institute used mathematical equations to develop a solar house that would be space-efficient, aesthetically pleasing and filled with light.Visitors break out the umbrellas as rain showers hit the area, just in time for the Solar Decathlon on the Mall. The homes will be open until Oct. 16, and the winner of the competition is to be announced Oct. 14.