I think the prior answer was correct.
"Nothing on a personal residence, not used in a business or as a rental, can be depreciated."
In states (e.g. Oregon) where the excess power sent back to the utility can onlyx be an offset to the power received from the utility, I don't think you can plausibly even argue that such an arrangement is a a trade or business for the homeowner.
In states where there is net metering and the utility buys back the power for cash, in theory the homeowner might argue that he/she is engaged in trade or business, but good luck with that argument if challenged by the IRS. In a typical residential solar installation in that situation, the homeowner's best case probably is relying on the audit lottery.
