This is tricky because the legal sites I use have the updated version of the law, not the version in place in 2022. Here is the instructions for form 5695 from 2022.
https://www.irs.gov/pub/irs-prior/i5695--2022.pdf
In a private letter ruling in 2018, the IRS ruled that a battery system was an allowable cost if it was connected in such a way that it was only charged by the solar system, and could not be charged from the utility. In other words, a battery used for "time-shifting" (when you have demand pricing) is not allowed prior to the Inflation Reduction Act in 2023, but a battery that is part of the solar system and can only be charged by the solar system, did qualify.
https://www.irs.gov/pub/irs-wd/201809003.pdf
Private letter rulings are not binding precedent on the IRS, but I would expect the IRS to follow the letter, since if you appealed to the Tax Court, the court is likely to use the same legal analysis.
