HVAC Section 179 Deduction: Limits, Phase-Out, and Recapture

An HVAC system installed in an existing commercial building can be fully expensed in the year it’s placed in service under the HVAC Section 179 deduction, up to a ceiling of $2,560,000 for tax years beginning in 2026. The deduction is only available for nonresidential buildings, only for systems added after the building was first placed in service, and only to the extent the business has enough taxable income to absorb it.¹

Which HVAC Installations Qualify

Section 179(e)(2) specifically names “heating, ventilation, and air-conditioning property” as qualified real property eligible for immediate expensing. To claim the deduction on an HVAC project, three things have to line up.¹

The building is nonresidential real property: an office, warehouse, retail space, or manufacturing facility.
The system is installed after the building was first placed in service. HVAC that goes in as part of a brand-new building’s original construction is treated as part of the building’s cost and can’t be separately expensed.
The property is purchased and used in an active trade or business. For mixed-use property, business use has to exceed 50%.

A rooftop unit replacement on a ten-year-old office building qualifies. A new split system dropped into a leased retail space qualifies. The HVAC package inside a ground-up new build does not, because it was never placed in service after the building itself.

Residential Rentals Generally Don’t Qualify

Landlords often assume Section 179 covers a new HVAC system in an apartment building or single-family rental. It usually doesn’t. The qualified real property provision that names HVAC applies only to nonresidential real property, so a central system in a residential rental is treated as a structural component of the building and depreciated over 27.5 years instead.¹

There’s one narrow exception. The Form 4562 instructions list portable air conditioners and heaters as tangible personal property eligible for Section 179.² A window unit or a portable space heater placed in a rental can qualify. A rooftop package unit or a central system cannot.

2026 Dollar Limits and the Phase-Out

The deduction has three ceilings stacked on top of each other for 2026.

Maximum deduction: $2,560,000 across all Section 179 property placed in service during the tax year, not just HVAC.
Phase-out threshold: once total Section 179 property placed in service exceeds $4,090,000, the maximum deduction is reduced dollar-for-dollar by the excess. A business that places $5,000,000 of qualifying property in service loses $910,000 of the deduction.
Complete elimination: at $6,650,000 of qualifying property, the Section 179 deduction zeroes out for the year.

Both figures adjust annually for inflation. The One, Big, Beautiful Bill made the higher limits permanent and indexed them going forward.²

The Business Income Limit

Section 179 cannot create a net loss. The deduction is capped at the taxpayer’s aggregate taxable income from all active trades or businesses. A company that earns $400,000 and installs a $600,000 HVAC system can only expense $400,000 in the current year; the remaining $200,000 carries forward and can be used in a future year with sufficient business income.¹

This trips up businesses whose HVAC project is large relative to the year’s profit. The deduction isn’t lost, but the tax benefit gets pushed into later years.

Section 179 vs. Bonus Depreciation

The One, Big, Beautiful Bill permanently restored 100% bonus depreciation for qualified property acquired after January 19, 2025.³ That might sound like it makes Section 179 redundant, but for most HVAC work it doesn’t.

Bonus depreciation applies to qualified improvement property, which covers interior improvements to nonresidential buildings. Exterior HVAC components, including rooftop units and condensers, sit outside the building envelope and aren’t interior improvements. For those items, Section 179 is the only route to immediate expensing. Interior HVAC work done as part of a broader interior renovation, such as new ductwork or interior air handlers, can qualify as QIP and be eligible for 100% bonus depreciation on that portion.

Beyond eligibility, the two tools differ:

Section 179 can’t reduce business income below zero. Bonus depreciation can create or increase a net operating loss, which then carries forward.
Section 179 has the $2,560,000 ceiling and the phase-out. Bonus depreciation has no dollar cap.
Both apply to new or used property, so long as it’s new to the taxpayer.

On a $1,200,000 rooftop HVAC replacement, Section 179 is the tool. If the same job includes $300,000 of interior ductwork, that portion may be broken out as QIP and run through 100% bonus depreciation instead. Contractor invoicing that clearly separates interior and exterior components makes the split defensible.

Recapture If Business Use Drops

Claiming Section 179 comes with an ongoing condition. If business use of the HVAC system falls to 50% or below at any point during what would have been its normal depreciation period, part of the deduction is recaptured as ordinary income.

The recapture equals the Section 179 amount originally claimed minus the depreciation that would have been allowable had the property been depreciated normally from the start. That difference is reported in Part IV of Form 4797, Sales of Business Property. After the recapture, basis in the property is increased by the recaptured amount.⁴

For a building used entirely for business, this rarely comes up. The exposure is real for mixed-use property, where changing tenants or a partial conversion can move the business share.

Claiming the Deduction on Form 4562

The election is made on Form 4562, Depreciation and Amortization, filed with the tax return for the year the system is placed in service. The election can be made on the original return or a timely filed amended return for that year.²

Part I of the form handles Section 179. The HVAC cost is entered under the qualified real property category, and the form walks through the dollar limits, the phase-out, and the income limitation. Any amount disallowed for lack of income carries forward automatically. The allowable deduction flows to the main return, whether that’s Form 1120 for a corporation, Schedule C for a sole proprietor, or the equivalent schedule for other entities.⁵

Keep the placed-in-service date, the purchase price, the contractor invoices showing what was installed, and, for mixed-use buildings, records supporting the business-use percentage. These matter if the IRS questions the deduction or if recapture is triggered later.

Section 179D Is a Separate Deduction

Section 179D sounds like a variant of Section 179 but is a different provision entirely. It provides a per-square-foot deduction for installing energy-efficient systems, including HVAC, in commercial buildings. The amount depends on how much the new system reduces the building’s total energy costs against a baseline, not on what the equipment cost.⁶

The HVAC installation has to achieve at least a 25% reduction in total annual energy and power costs compared to a reference building meeting ASHRAE Standard 90.1. The base deduction starts around $0.50 per square foot and scales up with greater savings, reaching about $1.00 per square foot at 50% savings. Projects meeting prevailing wage and apprenticeship requirements can reach roughly $5.00 or more per square foot.⁶

A high-efficiency HVAC installation can potentially claim both Section 179 and Section 179D, though 179D is capped at the lesser of the property’s cost or the per-square-foot calculation. A qualified energy consultant or engineer is typically needed to certify that the installation meets the required energy savings threshold.

1
Office of the Law Revision Counsel. 26 USC 179 – Election To Expense Certain Depreciable Business Assets
2
Internal Revenue Service. Instructions for Form 4562 (2025)
3
Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill
4
Internal Revenue Service. 2025 Instructions for Form 4797 – Sales of Business Property
5
Internal Revenue Service. About Form 4562, Depreciation and Amortization
6
Internal Revenue Service. Energy Efficient Commercial Buildings Deduction