Updated

They're trying to save the world — one house at a time.

Thousands of college students around the country have spent the past two years designing and building entire solar-powered homes to compete in the 2011 U.S. Department of Energy Solar Decathlon in Washington, D.C. later this year. The list of competitors was just whittled to twenty teams, who'll test the efficiency of their projects in a variety of contests later this year.

What’s the prize? Nothing more than bragging rights.

“Truly nothing but pride,” Amy Howard, project manager for the University of Tennessee’s Living Light team, told FoxNews.com. For their part in the competition, the team built an entire 850-square-foot house.

There's no solar-powered elevator, nor does photosynthesis fuel the kitchen. But the technology in the house is impressive nonetheless: Sensors in the walls detect changes in the outside light and automatically adjust the home’s inside lighting, for example. Glass walls help light it and a solar-paneled rooftop generates power during the day.

There's even a mobile app giving the user full wireless command over the house's numerous lighting and temperature settings. The system has an array of presets including all four seasons as well as morning, day, and night.

Howard said the $425,000 house uses roughly five to six kilowatts of power, which would be equivalent to burning a 100-watt light bulb for more than 50 hours.

Howard and her team have plans for their home other than just the competition. After they move the home to D.C., where it will sit on display at the National Mall for a few weeks in October, the team will bring it back to Tennessee for a tour throughout the Southeast region next year.

Students will use the home to teach the public about the design, the new technologies it incorporates, and various ways to conserve energy.

“We’re hoping to work with local schools to allow for tours during the daytime, but then also have it open for public visitation so that we can make the maximum use out of it — so we can really educate our fellow Tennesseans,” Howard said.

Others competing in the decathlon — like Team Florida, made up of members from the University of South Florida, University of Central Florida and University of Florida — had similar plans -- and similar neat technology.

An interior waterfall absorbs moisture from the air to control humidity, for example. And the group's "Flex House" will include smart appliances that talk to each other to prevent too many high-draw appliances from turning on at the same time, reducing spikes in demand on the grid.

Team Florida’s goal from the beginning, project manager Mario Rodriguez told FoxNews.com, was to bring their FlexHouse back to USF in Tampa and open it to the public as a learning center.

Students received $100,000 from the DOE but were responsible for raising any remaining construction costs that could not exceed $600,000. For Howard, the true prize of the competition was being able to showcase a house that could change how people live.

“Maybe the style isn’t exactly what they want or maybe they can’t afford to do a whole house,” she said, “but they can see the little tactics or the small technologies and innovations that they can actually implement."

"Over time they’re improving their lives," she said.