Hundreds of thousands of people have toured Solar Decathlon houses since the U.S. Department of Energy first held the contest in 2002, challenging college students to pair cutting-edge energy systems with architectural appeal and mass-market potential. The houses have been a huge hit in Washington, D.C., and have been installed permanently in locations from Darmstadt, Germany, to Beijing. But how much influence the decathlon has had on architecture or sustainable technology is more difficult to gauge—certainly it’s harder to measure than the houses’ kilowatt output.

Architects have admired the ingenuity with which many of the decathlon teams solved the challenges inherent in creating houses that not only power themselves but also are easy to transport. Perhaps because they’re so cutting-edge, though, none of the home designs has yet wowed builders into offering them on a wider scale, even though marketability is one of the 10 contests included in decathlon scoring. Housing markets, it seems, are more conservative than the student decathletes: Mike and Pete McKechnie, brothers who run a West Virginia green-energy company called Mountain View Solar & Wind, bought the University of Massachusetts at Dartmouth’s 2005 decathlon house and moved it to Berkeley Springs, W.Va., to use as a residence and demonstration home—but only after they added a second story and made the house look much more conventional.

The competition has, however, produced at least a couple of technological advances that have shown promise. The students who built Santa Clara University’s 2007 house worked with a civil-engineering professor, Mark Aschheim, to fabricate I-beam joists out of compressed bamboo floorboards. The innovation led to a 2010 paper in the Journal of Structural Engineering (published by the American Society of Civil Engineers), and it has encouraged Aschheim’s research in both sustainable construction materials and earthquake-resistant design. Meanwhile, successive University of Maryland teams have been perfecting an innovative dehumidifying system.

Indeed, the students participating in the competition have learned plenty while working on the homes. “These students live and breath this for two years,” says Richard King, who directs the decathlon program for the Energy Department. “The energy, the passion, the interest that they develop is not going to go away. You feel so much hope that they’re going to go on and change the world.”

The decathlon houses “all have some impact locally when they continue to be displayed and used,” King says; some are open for regular tours at science museums or on the campuses where they were built. The most famous is Virginia Tech’s 2009 Lumenhaus, which features a modular design in which a core unit equipped with solar panels and smart technology can be supplemented with inexpensive expansion modules as a family grows. The house, equipped with computer-controlled perforated-grid shade screens, was displayed this past summer beside the Farnsworth House, which Virginia Tech cited among its inspirations.

Rice University’s 2009 team created a contemporary solar-powered house that was designed to be moved to Houston’s Third Ward, a historic black neighborhood where it now houses artists-in-residence for Project Row Houses, an arts and cultural nonprofit. The team’s commitment to affordability impressed decathlon visitors and officials, particularly after the 2007 and 2009 competitions were won by sleek but very costly houses from the Technical University of Darmstadt in Germany. Partly because of the Rice team’s influence, decathlon officials adopted the affordability contest this year.

A few of this year’s teams also derived inspiration from Rice’s example of designing its house with a low-income community in mind. Purdue’s house will become home to a family in Lafayette, Ind., and the Parsons/Stevens team worked with Habitat for Humanity to relocate their house to Washington, D.C.’s Deanwood neighborhood. Those projects will certainly help the competition affect more real-world change.

Indeed, it’s the decathlon houses that are being lived in that serve as proof of the concept—and create the most effective and enthusiastic evangelists. Rex Barrick, physical-plant manager at the University of Texas at Austin’s McDonald Observatory in Fort Davis, rescued the university’s forgotten 2007 house and installed it on an old radio-telescope pad. The reliability of the electrical components, he says, “has given me a tremendous insight into being off the grid.” The students “did a tremendous job,” even though he’s had to complete a few projects they didn’t have time to finish. “An astronomical research facility is a great place for a house that runs off the sun,” he says. “I couldn’t think of anything more appropriate.”

Woody Woodroof, founder and executive director of the Red Wiggler Community Farm, lives with his partner in the 800-square-foot house that Maryland students designed for the 2005 competition. The house generates enough electricity to also power equipment for the farm. “We live in the house no differently than any other house that we’ve lived in, except that we’re much more mindful of the energy that we’re using,” Woodroof says. He admits to watching the house’s meter religiously.

Woodruff says the house has been changed only a little since the decathlon—its batteries were disconnected and it was instead hooked up to the power grid. Excess power generated during the day is sold to the local utility. “We make more power than we use,” he says, though not by much—meaning, he says, that the students designed an appropriately sized solar-powered system for the house.

Daniel Oerther, a professor of environmental engineering at the Missouri University of Science and Techology, shares a 2007 decathlon house on the university’s campus with his wife and their year-old son. The house, about 800 square feet, is located in a “solar village,” sitting beside the university’s other three entries. Two of those are rented to students, while the third is used as an office by students hoping to design the university’s next decathlon contender.

“The house has so much technology that you have to make conscious choices about how you use it,” Oerther says. “Are you trying to let light and heat in, or keep it out? Even when it’s freezing outside, it will get to 85 degrees inside just because of solar gain.” Paying such close attention to the house in turn “causes us to adjust the other things in our lives as well.” He and his wife have given up one of their two cars, eat less meat than they used to, purchase food locally when they can, and try to avoid toxic household cleaning products.

“I’m an environmental engineer,” Oerther says, “but I’ve always had a strong interest in our choices around where we live. We want to make choices with intention.” That doesn’t always mean they make good choices, he says, but at least they’re choosing, rather than being overwhelmed by the forces of marketing, peer pressure, and habit—forces that, he notes, have helped the average American house swell by about 500 square feet since 1980. “Solar-house living and small-home living are so much about intentional choices,” he says. “I think that’s what’s so powerful about the Solar Decathlon.”

Lawrence Biemiller is a senior writer at The Chronicle of Higher Education.