Some argue the cheapest kilowatt is the one you don't use -- meaning it's wiser to concentrate on conserving energy in your existing building rather than chucking it in favor of a new, green one [source: Robison]. If you're willing to investigate this possibility, start by hiring an energy performance company to evaluate your building's envelope. A building envelope is the space between a building's finished interior, which is heated and cooled, and the outdoors -- it includes components like walls, doors, windows, the roof and foundation [source: Wonderling]. You'll need to plug any leaky spots before installing photovoltaics (materials and devices that convert sunlight into electrical energy) and other upgrades. Yes, an evaluation and subsequent fixes may cost a few hundred dollars, but they may enable you to reduce energy consumption by as much as 40 percent per month [source: Robison.]
Once your building envelope is secure, dig into the small items. Some of the wisest energy conservation efforts include installing automatic lighting sensors, compact fluorescent light bulbs and solar-powered hot water heaters. Such minor changes can equal big bucks; research from the Lawrence Berkeley National Laboratory shows those automatic lighting sensors, which switch off lights when a room is unoccupied or when it's daylight, can save one-quarter to one-third of energy costs, and nearly 40 percent in buildings using multiple controls strategies [source: Williams et al.].
Once you've taken care of some of the easier, less time-consuming things, then you can consider larger-ticket items that require more than five years to pay off in savings. A large solar power system, for example, may be a wise investment -- or maybe not, depending how much you've pared down your energy consumption by some of the above actions. In the end, whether you build green or work on energy conservation, the main thing is that you're working to reduce energy use.