Solar power in Massachusetts has been increasing rapidly, due to for installations that began before December 31, 2011, and the sale of for $0.30/kWh, which allows payback for the system within 5 or 6 years, and generates income for the life of the system. For systems installed after December 31, 2011, and before December 31, 2016, the 30% tax grant becomes a 30% tax credit. There has.