It has been pointed out to me that IRS Notice 2013-70 does allow the buyer to claim the credit even if the builder installed the solar panels. The taxpayer must get a letter from the builder that breaks down the cost of the solar system, or the taxpayer must use some other "reasonable method" to determine what part of the home purchase price is the cost for the solar panel system. (However, be aware that if audited, the IRS will want to see proof of what your "reasonable method" was to calculate the cost.)
https://www.irs.gov/pub/irs-drop/n-13-70.pdf
As suggested by the other answer, individual states may offer their own credits and they may have different rules.
Some additional tips:
Although the credit is normally claimed when the property is "installed", in the case of new construction, the credit is claimed when the buyer's original use of the property begins. In other words, if the builder installed the solar panels in 2021 but you did not buy the home and move in until 2022, you would claim the credit on your 2022 tax return, not 2021.
You may not claim a credit for energy efficient doors, windows, HVAC, or other appliances installed by the builder. That credit is under a different section of the law (section 25C) and has different rules. That credit only applies to items you directly purchase and install to a home you already own.
And lastly, remember that if you receive a state or federal credit, that reduces your cost basis in your home, which is used to calculate capital gains when you sell.
