Net metering is what it sounds like. If you consume 10 kwh, but produce 5 kwhr, then the net is that you consumed 5. From your viewpoint, the meter "spins backwards" when the solar panels are producing. From the power company's perspective, they are both buying and selling at full retail price, which becomes a profitless business as more and more homes go solar. In the future, the power companies will want to pay less for the power you are putting into the system, so that they can make a profit. It's possible that instead of "netting", there will be inbound and outbound metering, at different rates. The treatment of cogeneration revenue is subject to state regulation, and can change at any time.