Idaho offers a tax deduction (not a tax credit) for solar panels!
The residential alternative energy tax deduction allows taxpayers an income tax deduction of 40% of the cost of a solar, wind, geothermal, and certain biomass energy devices used for heating or electricity generation. This can be applied in the year that the energy system is installed. 20% can be deducted each year for an additional three years. The maximum deduction in any one year is $5,000. The total maximum deduction is $20,000.
For more details, check out this resource and scroll down to Tax Credits and Deductions.