Consumers have heard for years that solar, wind, and geothermal power might soon cut their monthly energy bills. But things get exciting, even exotic, looking a decade or two ahead. Scientists envision that light bulbs will talk to switches, furnaces to windows, and everything to the Internet. Homes generate their own power in basement plants. Windows and paint change color to harvest sunlight or reject it. But ... cutting home energy use means changing consumer behavior and industry practice. That said, promising new technologies are emerging in labs, and some in commercial buildings, that in a decade or two could win over even the most skeptical builders and homeowners.