It depends.
If the dehumidifier is not permanently attached to the property and only keeps the property is good working condition, then you will be able to expense the cost as a repair in the current year.
Also, if the dehumidifier costs less than $500 then you will also be able to expense it whether or not the item is considered a repair or an improvement (the De Minimis safe harbor rule).
However, if the dehumidifier is a betterment to the property and provides this benefit for more than one year, you will need to capitalize these expenses. You will be able to claim an annual depreciation expense over the life of the capitalized assets.
According to the IRS, expenses that may result in a betterment to your property include expenses for fixing a pre-existing defect or condition, enlarging or expanding your property, or increasing the capacity, strength, or quality of your property are considered expenses that must be capitalized.
If your dehumidifier is fixing pre-existing moisture damage, then it will be considered a betterment of the property and you will need to capitalize these expense.
Please refer to this link for more information about rental income and expenses: ttps://www.irs.gov/taxtopics/tc414.html
Additionally, click Depreciation
of rental property for more information about depreciating a capital improvement.
