How The Tax Credit Works? Educate Yourself On The Credit
A tax credit is a dollar-for-dollar reduction in the income tax you would otherwise owe. For example, claiming a $1,000 federal tax credit reduces your federal income taxes due by $1,000. The federal tax credit is sometimes called an Investment Tax Credit, or ITC, though it differs from the ITC offered to businesses that own solar systems.
For more details
https://www.energy.gov/eere/solar/homeowners-guide-federal-tax-credit-solar-photovoltaics