Section 179 and Commercial HVAC: Why Treasure Coast Businesses Replace Before December 31
The short answer: Under Section 179 of the tax code, heating, ventilation and air-conditioning property installed as an improvement to an existing nonresidential building can be deducted in the year it is placed in service, instead of being depreciated over decades. For tax years beginning in 2026, the Section 179 limit is $2,560,000, with a phase-out starting at $4,090,000 of qualifying purchases. If your rooftop unit or split system is near the end of its life, a replacement that is installed and running by December 31, 2026 may count on this year’s return. Confirm the details with your CPA before you sign.
Key takeaways
- HVAC property added to an existing commercial (nonresidential) building is one of four named categories of “qualified real property” under Section 179.
- The 2026 limit is $2,560,000. The deduction phases out dollar for dollar once total qualifying purchases pass $4,090,000.
- The equipment has to be placed in service during the tax year. A signed proposal in December is not enough. The system has to be installed and operating.
- HVAC in residential rental property, including apartment buildings, does not qualify for Section 179 expensing.
- November is the realistic window. Equipment lead times, permits, crane scheduling and inspections all take time.
What Section 179 covers for HVAC
Section 179 lets a business deduct the cost of qualifying property in the year it goes into service. Building improvements usually do not qualify, because they are treated as part of the building and depreciated over 39 years. The exception is a short list of “qualified real property” improvements to nonresidential buildings placed in service after the building was first placed in service:
- Roofs
- Heating, ventilation, and air-conditioning property
- Fire protection and alarm systems
- Security systems
That means a replacement rooftop unit on a Stuart retail plaza, new split systems in a Jensen Beach medical office, or a new air handler in a Port St. Lucie warehouse office can be in scope. A brand-new building’s original HVAC is not, because the improvement has to come after the building was first placed in service.
The 2026 numbers
The One Big Beautiful Bill Act, signed in July 2025, raised the Section 179 limits and made them permanent, indexed for inflation. For tax years beginning in 2026:
| Item | 2026 amount |
|---|---|
| Maximum Section 179 deduction | $2,560,000 |
| Phase-out threshold (total qualifying purchases) | $4,090,000 |
| Business income limit | Deduction cannot exceed taxable business income; unused amounts carry forward |
For most Treasure Coast businesses, a full rooftop or split-system replacement sits well under the cap.
What about bonus depreciation?
The same 2025 law restored 100% bonus depreciation for qualified property acquired after January 19, 2025. Do not assume it covers your HVAC project. Rooftop and exterior HVAC units have been excluded from qualified improvement property treatment by the IRS, and many building systems are still 39-year property for bonus purposes. For a typical commercial AC replacement, Section 179 is the more direct route. Your tax advisor can confirm how your specific project should be classified, and Florida’s treatment can differ from federal.
Why “placed in service” is the date that matters
This is where year-end plans fall apart. The deduction follows the date the system is installed and ready to run, not the date you approved the quote or paid the deposit. For a commercial replacement, the timeline usually looks like this:
- Site visit and load review. We look at the existing equipment, the curb or pad, electrical, ductwork and controls.
- Proposal and equipment order. Lead times vary by tonnage and configuration. Some packaged units are in stock. Others take weeks.
- Permitting. Changeouts on the Treasure Coast generally require a mechanical permit from the city or county. We pull it.
- Install day. Rooftop jobs may need a crane, after-hours work, or a phased swap to keep you open. See what happens on installation day.
- Start-up, testing and inspection. The system is commissioned and the permit is closed.
Starting in November gives you room for a backordered part or a rain delay. Starting December 20 does not.
Is replacement the right call?
Taxes should not be the only reason to replace a working system. They are a good reason to stop putting off a replacement you already know is coming. Signs it is time:
- The unit is 15 or more years old, or it has had several major repairs in the last two summers.
- It still runs on R-22, which is no longer produced, so every leak repair gets more expensive.
- Coils and cabinets are corroded from salt air and the unit cannot hold temperature on peak afternoons.
- Your utility bills are rising while occupancy and hours are flat.
We cover the full decision in when to replace your commercial HVAC system and repair or replace your commercial air conditioner.
Three questions to bring to your CPA this month
- Do we have enough taxable business income in 2026 to use a Section 179 deduction, or should we carry it forward?
- Is this building nonresidential property, and is the HVAC an improvement to a building already in service?
- Should we elect Section 179, use bonus depreciation for any eligible components, or depreciate normally?
Then bring us in. We will give you an equipment proposal, a realistic install date, and an itemized invoice your accountant can work from.
Frequently asked questions
Does commercial HVAC qualify for Section 179? Yes, when it is an improvement to existing nonresidential real property. Heating, ventilation and air-conditioning property is one of the four categories of qualified real property named in Section 179.
What is the Section 179 limit for 2026? $2,560,000, with a phase-out that begins when total qualifying purchases exceed $4,090,000.
Do I have to install the new system by December 31 to deduct it this year? Yes. The property must be placed in service, meaning installed and ready for use, during the tax year you claim it.
Can a landlord with an apartment building use Section 179 for new AC units? No. Section 179 expensing for HVAC applies to nonresidential real property. Residential rental property does not qualify.
Does financing the system disqualify it? Generally no. Financed equipment can qualify if it is placed in service during the year. Confirm with your tax advisor.
Plan your replacement before the holidays
Sharkey Air installs and replaces commercial HVAC systems across Martin, St. Lucie and Palm Beach counties, from Fort Pierce to Palm Beach Gardens. Request a commercial replacement assessment or call (772) 220-2487. We will tell you what your equipment needs, what it costs, and whether we can realistically have it running before December 31.
This article is general information, not tax advice. Talk with a qualified tax professional about your situation.
Sources – U.S. Bank, Maximizing your deductions: Section 179 and bonus depreciation (2026 limit and phase-out): https://www.usbank.com/corporate-and-commercial-banking/insights/credit-finance/equipment/maximize-deductions-section-179.html – Wiss, A Refresher on the Section 179 Deduction (qualified real property categories, nonresidential requirement): https://wiss.com/section-179-deduction/ – UWorld, Section 179 vs. Bonus Depreciation, 2026: https://accounting.uworld.com/blog/cpa-review/section-179-vs-bonus-depreciation/ – CohnReznick, IRS excludes exterior HVAC units from special depreciation treatment: https://www.cohnreznick.com/irs-excludes-exterior-hvac-units-special-depreciation-treatment