Since 2002, the cost of installing a rooftop solar array has dropped from upward of $70,000 to about $18,000. That’s thanks in part to the Solar Decathlon, a Department of Energy competition that challenges college students to design and build mobile, energy-efficient houses. This month, Denver hosts the contest, giving the local squad (see “Rise House” below) a home-court advantage toward the $300,000 first-place prize. But the real rewards are the advancements the rest of us might see in our homes. Here’s a look at the legacy Colorado teams have built.

BASE+ House

The University of Colorado Boulder won the first Solar Decathlon in 2002 with a house designed to show that solar energy could be incorporated into any home. For example, the team sloped the roof at about 20 degrees less than the optimal 40-degree angle and aimed some of its panels in a southwest direction (rather than, ideally, south) to create a more realistic setup. Turns out the students were onto something; scientist Ronal Larson bought the 660-square-foot house and turned it into a 2,700-square-foot residence with heated floors and a 10,000-gallon water tank on Lookout Mountain.

Core House

As a part of the Solar Technology Acceleration Center (SolarTAC)—the nation’s only private solar testing facility—in Aurora, the 700-square-foot home CU Boulder’s team built for the 2007 competition has continued its work as a testing ground for new concepts. Xcel Energy, which funded the initial construction of Core House, has used it to troubleshoot technologies and identify problems early instead of facing public outcry later on. For instance, staffers modified some of the electrical switches after discovering they couldn’t handle frigid temperatures. “Making sure you have reliable power is great for summer days,” says Dustin Smith, SolarTAC’s executive director, “but it’s even more important when the Broncos game is on.”

Rise House

This year, 15 University of Denver students partnered with a University of California, Berkeley team that needed construction expertise to help make its blueprint a reality. The pairing was an ideal match since the 815-square-foot home addresses density and affordable housing issues—challenges both cities have grappled with. The unit can be stacked to create a multifamily complex fitted with inventive features such as sheep’s wool insulation and a moss wall that removes carbon dioxide from the air, all for about $200,000 or less.

If You Go

Tour the 12 innovative homes competing in this year’s Solar Decathlon
October 5 to 9 and 12 to 15
Near the 61st and Peña light-rail station