Residential Net Metering
Adding solar or wind power to your home, farm, or business not only means adding the solar panels, wind turbines, wiring, tracking equipment, etc.; but also means becoming familiar with the concept of "net metering". Net metering is the system by which a home or business that produces its own power can measure that power vs. what it consumes from a utility. So, a solar or wind powered home, which also draws power from the "grid" utility, will have a system which accounts for its own power production along with its power consumption. With net metering, the electricity meter supplied by the local utility will spin backwards should the power produced exceed the power consumed. Net metering allows a small power producer to push excess energy back into the utility grid, without having to install a battery system to store that excess power. Although one could install two separate meters to measure energy flow - one for the grid power being consumed, and one for the home-brewed power being produced - many small power installations are using a single, reversible meter.
Some utilities will not directly issue checks to a home or business that produces more power than it consumes. Instead, these utilities will issue credits toward future utility bills to their small power producing customers. In addition, utilities can avoid paying the full retail rate for home-brewed excess energy, compensating the small producer via the cheaper wholesale rate instead. It should also be noted that rural electric cooperatives and municipal electric utilities are not required to allow for net metering, although they might. Some net metering agreements require that a home or business not generate more than 25 killowatt-hours of electricity.
Each state has its own programs involving net metering and other energy use incentives. The U.S. Department of Energy has a state-by-state incentive database available here.