Sept. 22 marked the beginning of the fourth biennial Solar Decathlon, a collegiate green-building competition sponsored by the Department of Energy and located at the National Mall’s West Potomac Park. Over the course of two weeks, solar-powered houses from 20 teams will be judged by a panel of experts on their architecture, engineering, market appeal, hot-water generation, energy balance, and the ambiance of a dinner party that each house will host next week. For the first time, organizers will also evaluate structures by their affordability.

This year’s entrants, from 14 states and four countries, show distinct regional influences. Appalachian State, in Boone, N.C., calls its lean-to cabin “The Solar Homestead.” Team New Zealand, from Victoria University at Wellington, created amodernized “bach,” or traditional Kiwi beach house. Team Canada modeled its home on the teepees of the Native tribes in Southern Alberta, and had the chief of the Piikani Nation come to bless the site.

A spiritual philosophy also inspired Middlebury College’s gabled-roofed entry, “Self-Reliance,” named for an essay by New England transcendentalist Ralph Waldo Emerson. With its kitchen’s green wall and planter-lined deck, Self-Reliance exemplifies the holistic vision of sustainability shared by many of this year's teams. For example, the roof of Team Maryland’s Watershed, is designed after the ecosystem of the Chesapeake Bay, storing and filtering rainwater for reuse, while water from its showers and sinks filters to a deck-side water garden. 

Organizers will measure each team’s energy consumption and production for one week, with teams whose net balance is zero or better receiving 100 points. To try to minimize energy consumption and maximize energy generation, the City College of New York is using micro-inverters for each solar panel. Meanwhile, each team monitors its own consumption with intuitive interfaces. A joint team from SCI-Arc and the California Institute of Technology will keep tabs on its performance in real time with an iPad app.

The houses are open to the public, from 10 a.m.–2 p.m. on weekdays and 10 a.m.–5:30 p.m. on weekends. Visitors should be prepared for jostling crowds: event director Richard King said that over the 10 days of the 2009 competition, about 300,000 visitors came to peruse the houses.

Category winners for affordability will be announced on Sept. 27; engineering on Sept. 29; and communications on Sept. 30. Overall winners will be announced at an awards ceremony on Oct. 1.

Check for more information, including schedules for free workshops on renewable technologies.

And, if you’re in the market for a new energy-efficient home, put in an offer with teams’ publicists—although some homes, such as the City College of New York’s, will be returned to their institutions, and Parsons the New School of Design is donating its house to an Anacostia family through Habitat for Humanity. Team New Zealand’s “First Light House,” however, sold last week at an auction to a private buyer for $290,000.