Yes — a commercial HVAC system does qualify for bonus depreciation, but only when it meets the definition of Qualified Improvement Property (QIP). In practice that means a replacement, upgrade, or interior HVAC improvement placed in service after the building itself was first placed in service. For qualifying systems acquired after January 19, 2025, the One, Big, Beautiful Bill restored a permanent 100% first-year deduction.1Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One Big Beautiful Bill An HVAC system installed as part of a building’s original construction does not qualify, and instead depreciates over 39 years with the building.
What Makes an HVAC System Qualify
The path to bonus depreciation for commercial HVAC runs through Qualified Improvement Property. QIP is any improvement to the interior of a nonresidential building, provided the improvement is placed in service after the building itself was first placed in service.2Office of the Law Revision Counsel. 26 U.S. Code 168 – Accelerated Cost Recovery System Three types of interior work are carved out of QIP: expanding the building’s footprint, installing elevators or escalators, and modifying the building’s internal structural framework.
Applied to HVAC, the line is fairly clean. Replacing an aging air handler, swapping out ductwork, or dropping in a new rooftop unit that serves interior space all fit within QIP. Tearing out load-bearing walls to build a new mechanical room probably doesn’t, because that starts to look like structural framework.
The timing rule is what trips people up. If you construct a new office building and the HVAC goes in as the building opens, the system and the shell are placed in service together. The HVAC then defaults to the building’s 39-year recovery period, and bonus depreciation is off the table. That same equipment, installed a year later as a replacement, is QIP.
QIP itself carries a 15-year MACRS recovery period, restored retroactively by the CARES Act of 2020 after the 2017 Tax Cuts and Jobs Act inadvertently left it without one.2Office of the Law Revision Counsel. 26 U.S. Code 168 – Accelerated Cost Recovery System That 15-year classification is what gets QIP under the 20-year ceiling for bonus depreciation eligibility.
The 100% Rate and Why the January 19, 2025 Date Matters
Bonus depreciation had been phasing down under the TCJA schedule: 80% in 2023, 60% in 2024, 40% in 2025, with further cuts scheduled through 2027. The One, Big, Beautiful Bill scrapped that trajectory. For qualifying property acquired after January 19, 2025, the first-year deduction is 100%, and the provision is permanent under current law.1Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One Big Beautiful Bill
Read the acquisition date carefully. The cutoff is when the property is acquired, not when it is placed in service. An HVAC system ordered before January 20, 2025, but installed later can still fall under the old phase-down rates. For large projects with long lead times, the purchase commitment date is what you need to document.
What the Deduction Looks Like in Dollars
Under the current 100% rule, a $200,000 rooftop unit replacement that qualifies as QIP generates a $200,000 deduction in the year the system is placed in service. Nothing is left on the books to depreciate over the 15-year QIP schedule.
If the system was acquired before the January 19, 2025 cutoff and falls under the TCJA phase-down, the math has two steps. Apply the bonus percentage to the total cost, then depreciate the remainder over 15 years using standard MACRS. A $200,000 system placed in service in 2025 at the 40% rate produces an $80,000 bonus deduction, with $120,000 left to depreciate. Combined first-year recovery lands around $84,000.
Bonus depreciation can create or increase a net operating loss. That’s a meaningful advantage over Section 179 expensing, which can’t. If the HVAC deduction pushes the business below zero, the resulting NOL carries forward against future income.
You can elect out of bonus depreciation for an entire class of property by attaching a statement to a timely filed return. It’s all or nothing for that class — no partial election.
When QIP Doesn’t Apply: Section 179 as a Fallback
If an HVAC system misses QIP treatment (most commonly because it was installed as part of original construction), Section 179 offers a separate route to an immediate deduction. The statute specifically lists heating, ventilation, and air-conditioning improvements to nonresidential real property as eligible Section 179 property, as long as they’re placed in service after the building was first placed in service.3Office of the Law Revision Counsel. 26 U.S. Code 179 – Election to Expense Certain Depreciable Business Assets Note the same timing condition: original-construction HVAC still doesn’t qualify.
The statutory base for Section 179 is now $2,500,000, with the phase-out beginning at $4,000,000 in total qualifying property placed in service during the year.3Office of the Law Revision Counsel. 26 U.S. Code 179 – Election to Expense Certain Depreciable Business Assets Both figures are indexed for inflation. For 2026, the limit is approximately $2,560,000, with phase-out starting near $4,090,000.
The critical limit on Section 179 is that it can’t create a net operating loss. The deduction is capped at the business’s taxable income for the year. With $300,000 of taxable income and a $500,000 HVAC system, Section 179 caps you at $300,000; the unused $200,000 carries forward. Bonus depreciation has no such cap. For businesses with thin margins or large capital outlays, that difference usually decides the choice.
Section 179 requires an affirmative election on the return, and the election becomes irrevocable once the filing deadline (including extensions) passes. Where neither QIP status nor Section 179 applies, the HVAC system falls back to straight-line depreciation over 39 years.
Don’t Forget the Old System: Partial Disposition
Replacing HVAC involves disposing of an existing asset, not just installing a new one. The regulations allow a partial disposition election that lets you deduct the remaining undepreciated basis of the old system in the year you remove it.4eCFR. 26 CFR 1.168(i)-8 – Dispositions of MACRS Property Many owners miss this.
Suppose the original HVAC system had a $400,000 cost basis and $150,000 of accumulated depreciation. When you rip it out, the partial disposition election writes off the remaining $250,000 as a loss. Stack that against 100% bonus depreciation on the new system and you can generate a very large single-year deduction.
You make the election by reporting the loss on a timely filed return for the year of disposal — no separate form or election statement is required.5Internal Revenue Service. Examining a Taxpayer Electing a Partial Disposition of a Building The replacement asset is capitalized separately and must share the same asset class and recovery period as the disposed component. Records that identify the original cost and accumulated depreciation of the old system are what make this hold up on audit.
State Tax Doesn’t Always Follow Federal
Federal bonus depreciation and state treatment are frequently out of sync. A significant number of states either decouple from federal bonus depreciation entirely or cap the percentage at a lower rate. Where that’s true, the federal bonus deduction gets added back to state taxable income and the asset is depreciated over its normal recovery period for state purposes.
Over the asset’s full life, total deductions come out the same at both levels; it’s a timing difference. But in the year a major HVAC system goes in, state tax can be noticeably higher than a federal-only projection suggests. Section 179 conformity varies too, and some states apply their own lower dollar limits. Check your state’s conformity status before modeling after-tax returns on the project.
How to Report It
Bonus depreciation goes on IRS Form 4562, Depreciation and Amortization. Part II handles the special depreciation allowance; Line 14 is the primary line for the bonus deduction on qualified property.6Internal Revenue Service. Instructions for Form 4562 Any remaining basis flows into the standard MACRS sections of the same form.
Section 179 sits in Part I of Form 4562, with its own lines for the deduction, phase-out, and income limitation. You can’t claim both Section 179 and bonus depreciation on the same dollar of basis for the same asset, though you can use Section 179 on one HVAC project and bonus depreciation on another.
For the partial disposition on the old system, report the loss on Form 4797, Sales of Business Property. Keep detailed records of the disposed component’s original cost, accumulated depreciation, and adjusted basis at removal. The IRS flags partial dispositions as a common examination area, so documentation carries real weight here.7Internal Revenue Service. Cost Segregation Audit Technique Guide