me112233
Level 4

The safe harbor allows expensing for things that once required depreciating.  You can still depreciate a capital expenditure if you want to.

Regardless, in the scenario you provided, It's not that big a deal either way.  If you take it as an expense, the mini-split doesn't increase the basis, so more of the past depreciation will be recaptured at a more-or-less ordinary tax rate, BUT, your ordinary income from rental will be lower.    if you don't expense it, and just add it to the basis when calculating the cap gain in 2021, then rental (ordinary) income for 2020 will be higher than it would be if you expense the mini-split, BUT you will have a lower recapture of depreciation in 2021. 

Six or a half-dozen.  You choose.