Section 179D Is Gone: What the OBBBA Sunset Means for Your Rental Property Depreciation Strategy
For nearly two decades, Section 179D of the Internal Revenue Code rewarded building owners and designers for constructing energy efficient commercial and multifamily properties with a direct, dollar-per-square-foot deduction. As of July 1, 2026, that era is over. The One Big Beautiful Bill Act (OBBBA) closed Section 179D to any project where construction begins after June 30, 2026. If you own or are planning to build rental real estate, this change deserves your attention, not because most individual landlords ever claimed 179D directly, but because of what it signals and what now fills the gap it leaves behind.
This article explains what Section 179D actually did, who it applied to, exactly how the sunset works, and why the shift makes cost segregation and permanent 100% bonus depreciation more central to your tax strategy than ever.
What Section 179D Actually Was
Section 179D, originally enacted under the Energy Policy Act of 2005 and made a permanent part of the tax code by the Consolidated Appropriations Act of 2021, allowed owners of qualifying commercial buildings, and certain multifamily properties of four stories or more, to claim an immediate deduction for installing energy efficient systems. That included HVAC equipment, building envelope improvements, and interior lighting that reduced total energy and power costs relative to a reference standard set by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE Standard 90.1).
The Inflation Reduction Act of 2022 expanded the deduction significantly, lowering the efficiency threshold needed to qualify and increasing the maximum deduction, provided the project also met prevailing wage and apprenticeship requirements. By 2026, the maximum deduction available under 179D had climbed as high as $5.81 per square foot for the most efficient qualifying projects, a genuinely large number for a 100,000 square foot apartment building or office property.
Unlike cost segregation, which is available regardless of how a building performs energy-wise, 179D was a performance-based incentive. You had to design and certify the building to a specific efficiency standard, document it with an independent engineering study, and in many cases meet labor requirements to unlock the full deduction rate. It rewarded a specific kind of building, not a specific kind of taxpayer.
How the OBBBA Sunset Works
The OBBBA added a sunset provision to Section 179D that disqualifies any building where construction begins after June 30, 2026. The critical detail, and the one that trips people up, is that the cutoff is tied to the construction start date, not the placed-in-service date. A project that broke ground before the deadline remains fully eligible for the deduction even if it is completed and placed in service well into 2027 or later. A project that has not yet started construction as of July 1, 2026 is permanently locked out of 179D, regardless of how efficient the design is.
To be treated as having started construction before the cutoff, the IRS generally looks at whether significant physical work has begun on the project, or whether the taxpayer has incurred at least 5 percent of the total expected project cost and is maintaining continuous progress toward completion. Simply signing a contract or pulling a permit is unlikely to be enough on its own. If you are in the middle of a construction project right now and are counting on 179D, this is the moment to confirm with your general contractor and your tax advisor exactly when work began and whether your documentation supports that date.
The deduction is not limited to building owners. Architects, engineers, and design-build contractors who design energy efficient government buildings or buildings owned by tax-exempt entities such as nonprofits, schools, tribal governments, and religious organizations can also claim 179D directly, since those owners cannot use the deduction themselves. The owner issues an allocation letter to the designer of record. For firms that regularly design public buildings, the sunset removes a tool that has been part of standard project economics for years.
Who This Actually Affected
It is worth being honest about scope here. Section 179D was never a tool for the typical single-family rental owner or small landlord with a handful of duplexes and fourplexes. The deduction applied to commercial buildings and to residential buildings of four stories or more, which in practice meant larger multifamily developments, office buildings, industrial and warehouse facilities, retail centers, hotels, and similar commercial-scale assets. If your portfolio is single-family homes, condos, small multifamily under four stories, or short-term rentals, you were very likely never eligible for 179D in the first place, and its disappearance changes nothing about your available deductions.
Where the sunset matters is for developers, syndicators, and larger rental property investors building or substantially renovating mid-rise and high-rise multifamily, mixed-use, and commercial assets. For those investors, 179D has often been layered on top of cost segregation and bonus depreciation as a third source of first-year deduction, sometimes worth hundreds of thousands of dollars on a large ground-up development. Losing that layer changes the math on new construction decisions and shifts more of the tax planning weight onto the tools that remain.
The Tool That Survived: Permanent 100% Bonus Depreciation
Here is the important contrast. The same OBBBA that closed the door on Section 179D also permanently restored 100% bonus depreciation under IRC Section 168(k) for qualifying property acquired and placed in service after January 19, 2025, with no phase-down and no scheduled expiration. Unlike 179D, bonus depreciation does not care whether your building beats an ASHRAE efficiency benchmark. It does not require prevailing wage compliance, an independent energy model, or a specific building height. It applies to any qualifying tangible personal property and land improvement with a MACRS recovery period of 20 years or less, identified through a cost segregation study, regardless of the property's energy performance.
That is a meaningful structural difference. Section 179D rewarded efficient design choices with a deduction tied to building performance. Cost segregation combined with bonus depreciation rewards the acquisition or construction of the property itself, reclassifying components such as flooring, cabinetry, specialty electrical and plumbing, site improvements, parking areas, and landscaping out of 27.5-year or 39-year recovery periods under IRC Section 168(e)(2) and into 5-year, 7-year, or 15-year property. Every rental property owner has access to this tool. Almost none had access to 179D.
For an investor who was previously stacking 179D on top of cost segregation on a large multifamily project, the loss of 179D is a real reduction in total year-one deductions, and there is no way to fully replace that specific dollar amount. But for the much larger population of rental property owners who never qualified for 179D to begin with, nothing about your depreciation strategy has changed. Cost segregation and 100% bonus depreciation remain exactly as available and exactly as valuable as they were before the sunset.
What to Do If You Are Mid-Construction Right Now
If you have a commercial or multifamily project of four stories or more currently under construction, do not assume you have lost 179D eligibility just because the sunset headline is scary. Get specific documentation together now. Talk to your general contractor about the exact date physical construction began, and whether that date is documented in permits, site logs, or contractor invoices. If construction began on or before June 30, 2026, the project remains eligible for 179D at completion, and you should plan to commission both an ASHRAE-compliant energy study and a cost segregation study when the building is placed in service, since the two work together rather than against each other.
If your project has not yet broken ground, 179D is off the table regardless of how the building is designed. That does not mean energy efficient design no longer makes financial sense. Lower operating costs, stronger tenant demand, and utility rebate programs remain in play. It simply means the federal tax deduction that used to reward that design choice specifically is gone, and your depreciation planning should be built entirely around cost segregation and bonus depreciation instead.
What to Do If You Never Used 179D
If you own single-family rentals, short-term rentals, small multifamily, or any property under four stories, this entire news cycle is largely irrelevant to your personal tax situation, and that is worth saying plainly so you do not spend energy worrying about a deduction you never had access to. Your best available strategy remains what it has been since the OBBBA passed in mid-2025: acquire or improve the property, commission a cost segregation study to identify the components eligible for accelerated recovery periods, and apply 100% bonus depreciation to those components in the year the property is placed in service.
The practical numbers are still substantial without 179D in the picture. On a typical rental property, a cost segregation study commonly identifies 20 to 35 percent of the depreciable basis as 5-year, 7-year, or 15-year property. On a $500,000 property with $400,000 in depreciable basis, that might mean $100,000 to $140,000 in components eligible for immediate deduction under bonus depreciation. At a combined marginal tax rate in the 32 to 37 percent range, that translates into tens of thousands of dollars in reduced tax liability in the very first year of ownership, entirely independent of whether the building meets any energy efficiency standard.
A Reminder on Recapture and the Passive Loss Rules
None of this changes the underlying planning considerations that apply to any accelerated depreciation strategy. Components reclassified as 5-year and 7-year property are subject to IRC Section 1245 depreciation recapture, taxed as ordinary income when the property is sold. Fifteen-year land improvements fall under Section 1250 rules. And the resulting losses are still governed by the passive activity limitations of IRC Section 469, meaning whether you can use a large first-year deduction against non-rental income depends on your material participation status, your involvement as a real estate professional under Section 469(c)(7), or the short-term rental material participation tests. These rules did not change with the 179D sunset, and they remain the primary factors that determine how much immediate value you actually realize from any depreciation strategy.
The Bottom Line
The Section 179D sunset is a real loss for developers and owners of larger, efficiency-focused commercial and multifamily projects who had built it into their construction economics. If that describes you, get your construction start date documentation in order immediately and talk to your tax advisor about whether your current project still qualifies. For the majority of rental property investors, however, this is a headline about a deduction you likely never used, and it changes nothing about the value of a properly executed cost segregation study paired with permanent 100% bonus depreciation. That combination remains the single most powerful, broadly available depreciation tool for rental property owners in 2026, with or without Section 179D in the picture.