HVAC Depreciation Life: Recovery Periods, Bonus, and Section 179

A central HVAC system’s depreciation life depends on the building it serves: 27.5 years for residential rental property and 39 years for commercial (nonresidential) real property, both using the straight-line method under MACRS. Those timelines reflect IRS tax accounting, not the equipment’s physical lifespan. Commercial owners can often compress the schedule down to a single year through Qualified Improvement Property treatment, 100% bonus depreciation, or Section 179 expensing. Residential landlords generally cannot.

Why Classification Drives Everything

The IRS treats depreciable property as either personal property (shorter recovery periods) or real property (the building and anything structurally attached). Central HVAC systems, including furnaces, chillers, compressors, pipes, and ductwork, are structural components of the building. The IRS definition is explicit: all components of a central air conditioning or heating system are structural components, even those mounted on or adjacent to the building.¹ Being a structural component locks the system into the same long recovery period as the building.

The exception is portable equipment. Window air conditioners and portable space heaters placed in service after 2015 are tangible personal property in the five-year MACRS class.² If a unit plugs into a wall outlet and moves from room to room, it’s personal property. If it’s ducted, piped, or wired into the building, it’s structural.

Residential Rental: 27.5 Years

Any building where at least 80% of gross rental income comes from dwelling units is residential rental property. HVAC in that building depreciates over 27.5 years using the straight-line method.³ Straight-line spreads the cost evenly across the recovery period. A $10,000 furnace replacement produces roughly $364 per year in depreciation deductions.⁴

The first and last years are prorated using the mid-month convention. The IRS treats the system as placed in service on the 15th of the installation month. Install in March, and you get 9.5 months of depreciation in year one. Install in November, and you get 1.5 months.⁵

Residential rental HVAC does not qualify for Section 179 expensing, and it isn’t eligible for Qualified Improvement Property treatment, which is limited to nonresidential buildings. That gap catches many landlords off guard. The main lever left is the partial disposition election when replacing an old system, discussed below.

Commercial (Nonresidential): 39 Years, Usually Much Faster

Office buildings, retail spaces, warehouses, and any other commercial buildings that don’t meet the 80% dwelling-unit test are nonresidential real property. The default HVAC recovery period is 39 years, straight-line, mid-month convention.¹ A $50,000 commercial installation would otherwise yield about $1,282 per year.

Most commercial owners never actually use that 39-year schedule, because three provisions can collapse the deduction into year one.

Qualified Improvement Property (15 Years)

Qualified Improvement Property (QIP) is any improvement to the interior of a nonresidential building made after the building was first placed in service. An HVAC replacement that qualifies as QIP drops from a 39-year to a 15-year recovery period, and that reclassification makes it eligible for bonus depreciation and Section 179.¹

The key word is “interior.” Rooftop condensing units, compressors on exterior concrete pads, and other outdoor equipment are not QIP. The IRS has specifically ruled that HVAC units on a roof or adjacent to a building are not improvements to the interior portion. Indoor air handlers, ductwork, and furnaces installed inside the walls typically do qualify. The improvement cannot enlarge the building or alter its internal structural framework.

100% Bonus Depreciation (Now Permanent)

The One, Big, Beautiful Bill Act, signed in 2025, permanently reinstated 100% bonus depreciation for qualified property acquired after January 19, 2025.⁶ There is no scheduled expiration. For a commercial HVAC system placed in service in 2026 that qualifies as QIP, 100% of the cost can be deducted in year one rather than spread over 15.

One transitional note: for the first tax year ending after January 19, 2025, taxpayers may elect 40% (or 60% for property with longer production periods) instead of 100% if a smaller deduction is strategically preferable.⁶ That might fit a business expecting higher income in future years, but 100% is the default for most owners in 2026.

Section 179 Expensing

Section 179 lets a business expense the full cost of eligible property in the year it’s placed in service, up to annual dollar limits. For 2026, the maximum deduction is $2,560,000, with a phase-out that begins when total qualifying property placed in service exceeds $4,090,000.

HVAC systems in nonresidential buildings are specifically named as eligible for Section 179, alongside roofs, fire protection, and security systems. This eligibility applies even when the work doesn’t meet the full QIP definition.⁷ An exterior rooftop unit that fails the QIP interior test can still be fully expensed under Section 179, as long as the business is within the annual limits. Section 179 does not apply to residential rental HVAC.

Is It a Repair or an Improvement?

Not every HVAC expenditure needs to be depreciated at all. The IRS tangible property regulations draw a line between repairs (deducted immediately as business expenses) and improvements (capitalized and depreciated). Misclassifying the two is one of the most common and costly mistakes property owners make.

For this analysis, the IRS treats the HVAC system as its own unit of property, separate from the building structure and from other building systems like plumbing or electrical.⁸ You evaluate improvement questions by looking at the HVAC system alone, not the building as a whole. Replacing one component (say, a compressor) can be a repair relative to the entire system even if the dollar amount is substantial.

An expenditure must be capitalized if it meets any one of three tests applied to the HVAC unit of property:⁸

Betterment. The work fixes a pre-existing defect, adds materially to the system, or is reasonably expected to materially increase its efficiency, capacity, or output.
Restoration. The work replaces a major component or substantial structural part of the HVAC system, or replaces a component for which you’ve already claimed a loss deduction.
Adaptation. The work adapts the system to a new or different use from its original intended function.

Replacing an entire furnace or air conditioning system almost always triggers the restoration test. Replacing a thermostat, cleaning ducts, recharging refrigerant, or fixing a blower motor usually qualifies as a deductible repair. The gray area sits between: swapping a compressor in a multi-unit commercial system calls for a facts-and-circumstances analysis of whether that compressor is a “major component” of the whole.

For smaller expenditures, the de minimis safe harbor election lets you deduct items costing up to $2,500 each (or $5,000 if your business has audited financial statements) without going through the improvement analysis. You make the election on your return each year.

Claim a Loss on the Old System When You Replace It

Replacing an HVAC system is two events in one: installing new equipment and getting rid of the old. Before 2014, the tax code didn’t let you recognize the disposal. The old system’s undepreciated cost stayed on your books, generating phantom deductions on equipment sitting in a landfill.

The partial disposition election fixed that. When you replace a structural component like an HVAC system, you can elect to dispose of the old component and recognize a loss equal to its remaining undepreciated basis.⁹ If you installed a $20,000 system, depreciated $8,000, and then replaced it, you can claim a $12,000 loss on the disposed component in the year of replacement, in addition to starting depreciation on the new system.

The election is available for both residential rental and commercial property. It’s reported on Form 4797 and must be made on a timely filed return (including extensions) for the year of disposition. Many property owners and even some preparers overlook it, leaving real deductions behind.

Depreciation Recapture at Sale

Every dollar of depreciation claimed on an HVAC system reduces your tax basis. When you sell, the IRS claws back the benefit through depreciation recapture. For real property and its structural components, recaptured depreciation is taxed as unrecaptured Section 1250 gain at a maximum federal rate of 25%, higher than the long-term capital gains rate that applies to the rest of the profit.

This applies whether you used slow straight-line depreciation or expensed the full cost in year one through bonus depreciation or Section 179. Accelerated expensing doesn’t eliminate the tax; it shifts the timing. The upfront deduction is larger, and the recapture amount at sale is correspondingly larger. For owners planning to hold long-term or defer gain through a 1031 exchange, the upfront deduction is almost always worth taking. For a near-term sale, the trade-off needs a closer look.

Quick Reference by Scenario

New HVAC in a residential rental: 27.5 years, straight-line, mid-month convention. No bonus depreciation or Section 179.
Replacement HVAC in a residential rental: 27.5 years on the new system. Elect partial disposition on the old system to claim the remaining basis as a loss.
Interior HVAC replacement in a commercial building that qualifies as QIP: 15-year recovery, eligible for 100% bonus depreciation or Section 179. The full cost can be written off in year one.
Exterior rooftop unit on a commercial building: not QIP, but still eligible for Section 179 up to the annual dollar limit. Otherwise 39 years.
Portable window units or space heaters: five-year MACRS personal property, eligible for bonus depreciation and Section 179.¹
HVAC repair that doesn’t meet the betterment, restoration, or adaptation tests: fully deductible as a business expense in the year paid or incurred.

All depreciation is reported on IRS Form 4562 and must be claimed in the year the system is placed in service. Skipping depreciation doesn’t preserve the deduction for later. The IRS treats depreciation as “allowed or allowable,” so you lose the deduction for any year you skip it, and the basis reduction still applies when you sell.

1
Internal Revenue Service. Publication 946 (2024), How To Depreciate Property
2
Internal Revenue Service. Publication 946 (2024), How To Depreciate Property – Section: Which Property Class Applies Under GDS?
3
Internal Revenue Service. Publication 527 (2025), Residential Rental Property – Section: Table 2-1. MACRS Recovery Periods for Property Used in Rental Activities
4
Internal Revenue Service. Depreciation and Recapture 4
5
Internal Revenue Service. Publication 527 (2025), Residential Rental Property
6
Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One, Big, Beautiful Bill
7
Internal Revenue Service. Publication 946 (2024), How To Depreciate Property – Section: Qualified Section 179 Real Property
8
Internal Revenue Service. Tangible Property Final Regulations – Frequently Asked Questions
9
Internal Revenue Service. Examining a Taxpayer Electing a Partial Disposition of a Building