The Department of Energy's New Net-Zero Building

The United States Department of Energy has just completed the nation's largest net-zero energy building. This 222,000 square-foot structure, a "Research Support Facility" on the NREL campus in Golden, Colorado, uses 50 percent less energy than a conventional building and produces what energy it does need with on-site solar panels.

The cost to build it was high—$259 per square foot—and it looks like you'd have to drive to get there, but it's still a remarkable example of just how much one can do with natural light, smart controls, and solar power. Despite being a monster, this building could be completely off the electric grid.