Designed by students, the small blue house wedged onto a corner of the Santa Clara University campus generates all the electricity it needs. And it needs very little. Solar cells blanket most of the roof. A separate solar array heats water. Pipes in the ceiling circulate cold water to keep the house cool. A mobile phone app controls the lights and windows. Dubbed Radiant House, the building is the university's entry in this year's Solar Decathlon, an international student competition to create energy-efficient houses that run their systems and appliances on sunlight. To win, the houses can't just be a collection of technologies. They have to feel inviting and livable. Judges grade them on comfort and curb appeal in addition to innovation. This year's decathlon culminates next month in Orange County, when 20 university teams present their homes to judges drawn from the fields of architecture, development and renewable energy. First held in 2002, the Solar Decathlon runs in two-year cycles, giving teams enough time to design, finance and build their creations. This year, students from two Bay Area schools - Santa Clara and Stanford University - will compete against teams from as far afield as Austria and the Czech Republic. The contest rules require that the houses can't be larger than 1,000 square feet and must produce at least as much energy as they consume over the course of a week. Solar panels donated by Bosch Solar Energy coat the central room's tilted roof and can generate up to 7.14 kilowatts of electricity, more than a typical home array. The panels rest on a new type of rack, made by startup company Sunplanter, that is integrated into the structure of the roof.