Section 179D Deduction: Qualifying Buildings, Amounts, and Claiming

The Section 179D deduction lets owners of commercial buildings — and, in some cases, the architects or engineers who designed them — write off the cost of energy-efficient improvements against federal income tax. After the Inflation Reduction Act of 2022, the deduction runs from roughly $0.58 up to $5.81 per square foot for property placed in service in 2025, with the top figures available only when prevailing wage and apprenticeship standards are met. It applies to new construction, upgrades, and, through a separate pathway, retrofits of older buildings.

Which Buildings Qualify

A building is eligible if it sits in the United States and falls within the scope of ASHRAE Standard 90.1, the national benchmark for energy-efficient building design.¹ That standard covers virtually all commercial and institutional buildings: offices, retail, warehouses, hospitals, schools, hotels. It also covers residential buildings of four or more stories, because ASHRAE 90.1 excludes only low-rise residential construction of three stories and under.² A five-story apartment building qualifies. A three-story townhome complex does not.

The property being deducted must be depreciable or amortizable, and it must be installed as part of the building’s interior lighting, heating and cooling systems, hot water systems, or building envelope — the roof, walls, windows, and insulation that separate the interior from the outside.³

Who Can Claim It

Private building owners claim the deduction directly. Install a more efficient HVAC system or upgrade the lighting in a commercial building you own, and the deduction reduces your taxable income for the year the improvements are placed in service.

Tax-exempt owners have no federal income tax to offset, so the statute lets them allocate the deduction to the designer primarily responsible for the energy-efficient features. The definition of a “specified tax-exempt entity” is broad: federal, state, and local government agencies, Indian tribal governments, Alaska Native Corporations, and any organization exempt from federal income tax.¹ That last category sweeps in nonprofits, public universities, and houses of worship. The designer receiving the allocation is typically an architect, engineer, or design-build contractor.

The allocation must be in writing, signed by both sides, and must include a penalty-of-perjury statement from the building owner’s authorized representative along with the building address, cost of the energy-efficient property, placed-in-service date, and the dollar amount being allocated.⁴ A defective allocation letter can sink the deduction, so designers should treat it with the same care as the tax return.

The 25 Percent Energy Savings Threshold

Qualifying improvements must cut the building’s total annual energy and power costs by at least 25 percent compared to a reference building that barely meets ASHRAE Standard 90.1.³ An energy modeler runs two simulations: the actual design and a bare-minimum code-compliant twin. The gap between their projected energy costs determines whether you clear the 25 percent bar.

The IRS periodically updates which edition of ASHRAE 90.1 serves as the reference. For buildings placed in service through the end of 2026, the reference standard is ASHRAE 90.1-2007.⁵ That older edition sets a relatively low baseline, which makes it easier for modern designs to clear the threshold. Buildings whose construction began before January 1, 2023, may also use the 2007 edition regardless of when the property is placed in service.

How Much the Deduction Is Worth

The deduction is measured against the square footage of the building area served by the qualifying improvements, and the rate scales with energy performance.

Base Amounts

The statutory base is $0.50 per square foot at exactly 25 percent energy savings, rising by $0.02 for each additional percentage point of savings, up to $1.00 per square foot at 50 percent savings.¹ Those figures are indexed for inflation starting in 2023. For 2025, the IRS published inflation-adjusted base rates of $0.58 to $1.16 per square foot.⁶

Bonus Amounts

Projects that satisfy prevailing wage and apprenticeship requirements earn roughly five times the base. The statutory bonus starts at $2.50 per square foot at 25 percent savings, climbs by $0.10 per additional percentage point, and caps at $5.00 per square foot at 50 percent savings.¹ After inflation adjustments, the 2025 bonus rates run from $2.90 to $5.81 per square foot.⁶ On a 100,000-square-foot building hitting the maximum savings target, that is the difference between roughly $116,000 (base) and $581,000 (bonus). The labor compliance costs are almost always worth it.

Basis Reduction

Claiming the deduction comes with a trade-off. You must reduce the depreciable basis of the property by the amount of the deduction you take.⁷ That means less depreciation in future years. For most taxpayers the immediate deduction still wins by a wide margin, but on marginal projects, run the numbers.

Prevailing Wage and Apprenticeship

The bonus deduction requires two sets of labor standards during construction.

Under the prevailing wage rule, every laborer and mechanic on the project — whether working for you, a general contractor, or a subcontractor — must be paid at least the prevailing wage rate for their trade and geographic area, as determined by the Department of Labor under the Davis-Bacon Act.⁸

The apprenticeship rule has three parts. At least 15 percent of total labor hours must be performed by qualified apprentices from registered apprenticeship programs. The apprentice-to-journeyworker ratio must meet the standards of the relevant program each day. And any contractor or subcontractor employing four or more workers on the project must hire at least one qualified apprentice.⁸ Apprenticeship requirements apply only to work performed before the building is placed in service; post-occupancy repairs and alterations are not subject to them.

If a worker was paid below the prevailing wage, you can preserve the bonus by making a correction payment (the shortfall plus interest at the federal short-term rate plus six percentage points) and paying a $5,000 penalty for each underpaid worker within 180 days of a final IRS determination. Intentional failures triple the correction payment and double the penalty.⁹

The Retrofit Pathway

The Inflation Reduction Act added an alternative deduction for retrofitting older buildings. Rather than modeling energy savings with software, this pathway uses metered energy data before and after the work.

The building must have been originally placed in service at least five years before you establish a qualified retrofit plan.¹ After the work is complete and the building has operated for more than a year, you compare the measured site energy use intensity before and after. The improvements must reduce energy use intensity by at least 25 percent in aggregate.⁷

Per-square-foot amounts and the prevailing wage bonus mirror the modeling pathway. The practical difference is timing: because you need more than a year of post-retrofit data before certification, the deduction lands on your return well after construction wraps up.

Claiming It More Than Once on the Same Building

Before the Inflation Reduction Act, a building could generate the 179D deduction only once. Current rules allow the deduction to be claimed again after subsequent energy-efficient improvements, generally every three tax years. That makes 179D useful for phased upgrade programs where lighting comes first and mechanical systems follow a few years later.

Third-Party Certification

You cannot claim the deduction without a third-party certification confirming the energy savings. The certifier must be a qualified individual recognized by an organization the IRS has approved for this purpose,³ in practice usually a licensed professional engineer or registered architect who runs the energy model and inspects the installed systems.

For the modeling pathway, the certifier uses software from the Department of Energy’s approved list.¹⁰ The certification must explain the building’s energy efficiency features and its projected annual energy costs.³ For the retrofit pathway, the certifier works with actual metered energy data, adjusted for weather differences between the pre- and post-retrofit periods.⁷

How To Claim the Deduction

The deduction is claimed for the year the qualifying property is placed in service, meaning the year it is ready for its intended use. The primary form is Form 7205. You calculate the deduction, identify yourself as owner or designer-allocatee, report the certifier’s information, and document the allocation details.¹¹ The amount flows through to your income tax return: Form 1120 for corporations, Form 1040 for individuals and pass-through owners.

The numbers on Form 7205 must match the third-party certification exactly; inaccurate energy modeling can trigger civil penalties. Hold onto the certification report, the allocation letter (if you are a designer), all energy modeling files, and prevailing wage records for at least three years after filing.¹²

Prior-Year Property You Never Claimed

If you placed qualifying property in service in an earlier year but did not claim the deduction, you do not have to amend each old return. File Form 3115 to request a change in accounting method under the automatic procedures, using designated change number 152.¹³ That picks up the entire missed deduction in the current year as a catch-up adjustment, with no user fee and no wait for IRS approval. Form 3115 is technical, so bringing in a tax professional experienced with 179D is worth the cost.

1
Office of the Law Revision Counsel. 26 U.S. Code 179D – Energy Efficient Commercial Buildings Deduction
2
ASHRAE. Standard 90.1-2022 – Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings
3
Office of the Law Revision Counsel. 26 USC 179D – Energy Efficient Commercial Buildings Deduction
4
Internal Revenue Service. IRC 179D Energy Efficient Commercial Buildings Deduction
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Internal Revenue Service. Updated Reference Standard 90.1 for 179D
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Internal Revenue Service. Energy Efficient Commercial Buildings Deduction
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Department of Energy. 179D Energy Efficient Commercial Buildings Tax Deduction
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Internal Revenue Service. Frequently Asked Questions About the Prevailing Wage and Apprenticeship Under the Inflation Reduction Act
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Federal Register. Increased Amounts of Credit or Deduction for Satisfying Certain Prevailing Wage and Registered Apprenticeship Requirements
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Department of Energy. Qualified Software for Calculating Commercial Building Tax Deductions
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Internal Revenue Service. About Form 7205 – Energy Efficient Commercial Buildings Deduction
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Internal Revenue Service. Topic No. 305, Recordkeeping
13
Internal Revenue Service. Revenue Procedure 2025-23