Federal Solar Tax Credits

The "Federal Investment Tax Credit" covers 30% of equipment and installation costs for solar PV systems. The tax credit is unlimited, applicable to the tax-year the system is placed into service, and remaining credits may be carried back 1 year (up to 50% of total) and/or carried forward until exhausted, for up to 15 years. (IRS Form 3468). In the year 2020, the tax credit steps down to 26 percent and 22 percent in 2021. After 2023, the residential credit will drop to zero while the commercial and utility credit will drop to a permanent 10 percent.

https://www.irs.gov/uac/form-3468-investment-credit-2