A typical 6 kW home solar system in Maine costs about $19,440 before incentives, or roughly $13,608 after the 30% federal tax credit.
Local pricing and sun hours change the math. Size your system and estimate cost in the solar cost calculator and system size calculator.
The 30% federal credit applies everywhere (see the tax credit calculator); Maine may add state or utility incentives. Check payback against your electric rates in the savings calculator.