Incentives and rebates vary, with some being offered for limited time. In general, the Investment Tax Credit (ITC) has been extended through 2019. Other credits such as the Mass. state managed SRECs and other purchase incentives such as Solarize programs are not as consistent. Look further through the links below for more current and up to date information:

Massachusetts
Massachusetts Clean Energy Center
Mass.Gov – Energy & Environmental Affairs
CleanEnergyAuthority.Com – Rebates & Incentives (MA)

Rhode Island
Rhode Island – Office of Energy Resources
CleanEnergyAuthority.Com – Rebates & Incentives (RI)