The 30% tax credit for the cost of buying and
installing a solar system is available for 2018 and 2019. For 2020 the credit
drops to 26%, for 2021 the credit drops to 22%, for 2022 the credits fall all
way down to 10%, for 2023 the 10% credit is only for companies that install and
maintain solar systems and sell the power to another entity (homeowner,
business, utility company, etc.)
The federal solar tax credit (residential energy
credits - Form 5965) is a tax credit, not an itemized deduction.
So, it won't be affected if you stop itemizing your deductions. You
will still be able to take advantage of this credit even without itemizing.
But, it is limited to tax liability. However, you can carry it forward
to future years when you aren't able to use up the tax credit in one year.
Note: Technically, the IRS has not clarified how long the carry
forward will be available to use. As of now, the carry forward should be
available until 2022, at least, because the tax credit was recently extended
until that time. So, it's possible that the IRS could stop allowing the
carry forward at that time. Also, you will need to file the Form every
year even if you aren't able to use any of the tax credit in order to keep the
credit carrying forward.