Replaced complete HVAC system - improvement or expense?

[MiriamF]

It depends.

If you replaced this HVAC system in your primary residence or a rental property, then it adds to the basis of your home. The basis becomes important only if you sell your house. For a rental property, it also adds to the depreciation.

If the HVAC system fits the government definition of an energy-efficient system, then it is a deductible expense, eligible for a residential energy credit.

More details about residential energy credits can be found in this article.