This is a problem that has been solved many times and is (relatively) inexpensive. It is called a "grid tie" power inverter, commonly used with solar panels.

This is a problem that has been solved many times and is (relatively) inexpensive. It is called a "grid tie" power inverter, commonly used with solar panels. http://www.affordable-solar.com/grid.tie.htm http://www.affordable-solar.com/grid.tie.htm http://www.affordable-solar.com/solar.inverters.grid.tied.htm http://www.affordable-solar.com/solar.inverters.grid.tied.ht...