An FAQ on net metering from Earth2Tech:
The U.S. electrical grid is one of the most regulated and least sophisticated networks out there. Of course buying power off of the grid is easy enough, but what if you want to try to sell electricity back to the grid? It might not be too easy to simply sell your excess juice from your solar panels, depending on where you live. Hereâ€™s a primer on the issue of â€œnet meteringâ€ and how it will allow individuals to power the grid.