The tax deductibility of a new AC unit depends on several factors. Generally speaking, if you are replacing an old AC unit with one that has similar specifications and serves the same purpose, it would likely be considered a repair or maintenance expense and would not be tax deductible. However, if you are installing a new AC unit that improves energy efficiency and meets certain qualifications outlined by government programs such as Energy Star, you may be eligible for tax credits or rebates that can help offset some of the costs associated with purchasing and installing the unit. It's advisable to consult with a tax professional or research IRS guidelines to understand what specific requirements must be met to potentially claim any deductions related to a new AC unit on your taxes.