Several states have introduced Feed-in-tariff, which pays you for selling electricity to grid. The two common Feed-in-tariifs are
Under Net feed-in-tariff, a premium is paid for any surplus energy generated by your solar panels. You get credits for selling excess power to grid and it will offset against your electricity bill.
Under Gross Feed-in-tariff you get paid for every unit of electricity generated by your solar panels. Regardless of whether it goes into the grid or it is used by your household.