From the Department of energy
Selling Power to a Utility
The Public Utility Regulatory Policies Act (PURPA) of 1978 requires electric utilities to purchase power from independent power producers if certain conditions are met. You will need to contact your local utility and/or public utility commission to determine what these technical and operating requirements are, and the price that the utility will pay you for the electricity you generate. You may also need a license from FERC. The utility will require that you insure the system. The interconnect requirements and insurance premiums may cost more than what you earn from selling the power. An alternative to selling power is "net metering or billing," where your system offsets the amount of power you purchase from a utility. Many states in the USA have net metering provisions, however, you will still have to negotiate with the utility concerning their interconnection requirements. (See EREC's information brief "Connecting a Small-Scale Renewable Energy System to an Electric Transmission System."
Some helpful links
http://www.eere.energy.gov/consumeri...riefs/ab2.html
and
http://search.nrel.gov/query.html?qp...=selling+power