Did you know you can cut your water use by 10 gallons a day by switching toilets? That a new washer and dryer could save you almost $150 a year? These are just two of the dozens of tips, tricks, facts and projects packed into the free Green Home Guide, the second in our series of digital special issues called Genius Guides, designed to make you an expert on one of the core PopSci topics. You can click through our animated home to see the worst spots for wasting power, air and water. Or explore our interactive map to get energy cost and CO2 stats for each of the 50 states. We've also got stories of three ambitious homeowners who have taken energy savings to extremes, heating their house with a room full of sand or powering it with a waterfall.