Install solar electric power system before the end of 2020, you can claim 26 percent of the installed cost as tax credit. The federal tax credit has started phasing out with 22% for year 2021 and 0% for year 2022
As a credit, you take the amount directly off your tax payment, rather than as a deduction from your taxable income. You can claim the credit for your primary residence, a vacation home, and for either an existing structure or new construction. Other than the cost of the system, there's no limit to the dollar amount of the credit.
For commercial, there is business depreciation where you can recover the cost of the system in less than 5 years. Contact your CPA.