Thanks so much for the response!
I'm not sure I agree with your analysis of Sec. 179... bonus depreciation yes, but not Sec. 179.
My understanding is that with residential rental property (e.g., a 10 unit apartment building, all units with 1 year lease terms), as opposed to commercial property if the property being replaced, is personal property (e.g., a refrigerator, NOT an HVAC unit...my mistake on choosing HVAC for my question), we can claim Sec. 179. I don't think that, in general, HVAC is considered personal property and that is why the authors of those cited articles seem to be wrong, or did a poor job of not explaining fully what they were trying to say.
It used to be that Sec 179 was never available for rental property owners to use to deduct the cost of personal property in residential rental units. However, in a victory for landlords, the TCJA eliminated this restriction starting in 2018.
As of this point, I think the question is whether replacing 5 out of 10 AC units would be considered a repair...putting Sec. 179 aside. And I'd like a sanity check on the following example in the Regs Sec.1.263(a)-3(k) (7) Example 18.
3 of 10 roof-top HVAC units must be replaced and can be treated as deductible repairs.
"The three roof-mounted heating and cooling units are not a significant portion of a major component of the HVAC system under (k)(6)(ii)(A) of this section, or a substantial structural part of the HVAC system, under paragraph (k)(6)(ii)(B) of this section. Accordingly, O is not required to treat the amount paid to replace the three roof-mounted heating and cooling units as a restoration of the building..."
5 out of 10 is much more than 3 out of 10 so it may not be "too gray" that these 5 units must be capitalized.
