The U.S. Department of Energy-sponsored Solar Decathlon pits 20 teams from around the world against each other in a contest to build the best solar-powered house. The teams have three weeks to assemble their houses, which are mostly constructed ahead of time at a different location. The houses, which line the National Mall in Washington, D.C., must be fully functional and are open for the public to tour throughout the contest. The houses are judged on a variety of factors including how attractive, effective, and energy efficient they are. Teams receive points for their houses in ten different contests and a winner will be selected at the end. The houses will stand on the National Mall until October 21.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

Twenty teams representing nations and universities from around the globe met in Washington to compete in the Solar Decathlon.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

A student from the Universidad de Puerto Rico cleans his house’s solar panels to maximize their efficiency during the daylight.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

Students from the University of Wisconsin-Milwaukee assembled their house earlier in the month in preparation for the contest.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

The Penn State team’s house features a “living wall” in the kitchen where spices and herbs can be grown.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

The houses were opened to the public on October 9.

Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon

The house of Germany’s Technische Universität Darmstadt, features a solar-powered toy windmill.

By Elizabeth Wolfe