solar tiles that would meet your entire house's energy demands and would also water your lawn and clean your gutters while they were up there. But, despite pledges of "affordability" something tells us it'll be awhile before your roof starts juicing your gadgets. This solution from MIT looks a little more practical -- and affordable. They're simply tiles that change color based on the temperature, Hypercolor style. In the cold they turn jet black, absorbing the sun's warmth and channeling that into the house. In heat they turn white, reflecting that same light and cutting down on cooling bills. Simple and smart. The MIT team calls the tech Thermeleon, and while early prototypes do change color as designed, it remains to be seen how durable the tech will be, and a leaky roof is no good regardless of how efficient. Asphalt shingles reign supreme for yet another year.