Section 179D: The Energy Efficient Commercial Building Deduction
Section 179D rewards building owners and designers who build or retrofit commercial buildings to high energy efficiency standards. The IRA tripled the maximum deduction and opened it up to architects, engineers, and contractors designing buildings for governments, nonprofits, and tribal nations — a group previously excluded from the program.
Overview and IRA Changes
Before the IRA, Section 179D provided a maximum deduction of $1.80 per square foot for commercial buildings achieving at least 50% energy reduction versus ASHRAE 90.1-2007. The IRA made sweeping changes effective January 1, 2023:
- Maximum deduction increased to $5.00/sq ft for buildings satisfying prevailing wage requirements
- Base deduction is $1.00/sq ft without prevailing wage (versus $1.80 previously)
- Expanded the "designer" rule to allow the deduction to be allocated to architects, engineers, and contractors for buildings owned by any tax-exempt entity (not just government)
- Revised energy baseline from ASHRAE 90.1-2007 to the most recent ASHRAE 90.1 standard in effect 2 years before construction begins (for projects beginning after 2022)
- Deduction is now available annually (not just once per building) for improvements
Deduction Rates: $0.50 to $5.00 Per Square Foot
The deduction is calculated on a sliding scale based on the percentage of energy reduction achieved compared to the ASHRAE baseline:
| Energy Reduction | Without PWA | With PWA |
|---|---|---|
| 25% (minimum threshold) | $0.50/sq ft | $2.50/sq ft |
| 30% | $0.60/sq ft | $3.00/sq ft |
| 40% | $0.80/sq ft | $4.00/sq ft |
| 50%+ (maximum) | $1.00/sq ft | $5.00/sq ft |
Note: Rates are subject to annual inflation adjustments. The $5.00/sq ft rate assumes projects meeting prevailing wage requirements. Rates shown are approximate 2026 values before inflation adjustment.
Eligible Buildings
Section 179D applies to:
- Commercial buildings (office, retail, industrial, warehouse, hotel, hospital)
- Residential rental buildings of 4 or more stories
- Government-owned buildings (federal, state, local, territory)
- Buildings owned by tax-exempt organizations (nonprofits, hospitals, universities, churches)
- Buildings owned by Indian tribal governments
Who Can Claim It: The Designer Allocation Rule
For commercial buildings owned by taxable entities (private owners), the building owner claims the 179D deduction directly.
For buildings owned by tax-exempt entities (nonprofits, governments, tribal nations), the IRA allows the building owner to allocate the deduction to the architect, engineer, contractor, or energy services company that designed the energy-efficient features. This creates a powerful incentive structure: the designer can monetize the deduction in exchange for providing better energy performance, often sharing the benefit with the building owner through reduced design fees or energy performance guarantees.
Key requirement: The designer allocation must be made through a written statement signed by the owner of the building (or an authorized representative) before the deduction is claimed. The statement must identify the building, the tax year, and the portion of the deduction allocated.
Partial Deduction: Three Qualifying Systems
If a building cannot achieve the 25% whole-building energy reduction required for the full deduction, partial deductions are available for each of three systems independently:
Interior Lighting
25% reduction in lighting power density vs. ASHRAE 90.1-2007
This is the most commonly achieved partial deduction — LED upgrades often qualify
HVAC and Hot Water Systems
Meet applicable ASHRAE 90.1-2007 HVAC efficiency requirements
Requires detailed energy modeling; HVAC improvements alone may not meet the 25% threshold
Building Envelope
Meet applicable ASHRAE 90.1-2007 envelope requirements
Insulation, windows, and roof improvements; hardest to achieve independently
Example: 50,000 Sq Ft Office Building
Scenario: Class A office building, new construction, ASHRAE 50% energy reduction, prevailing wage compliant
At a 35% marginal tax rate, this $250,000 deduction translates to approximately $87,500 in direct tax savings. For a government building, the architect or engineer who designed the energy systems can claim this deduction directly through the allocation mechanism.
Frequently Asked Questions
What is the maximum Section 179D deduction per square foot?
The maximum 179D deduction is $5.00 per square foot for buildings placed in service after December 31, 2022, that satisfy prevailing wage requirements. Without prevailing wage, the maximum is $1.00 per square foot. The actual deduction ranges from $0.50 to $5.00/sq ft depending on the percentage of energy reduction achieved versus the ASHRAE 90.1-2007 baseline, subject to inflation adjustments.
Who can claim the 179D deduction for government and nonprofit buildings?
Prior to the IRA, only taxable building owners could claim 179D. The IRA created a new pathway: for energy-efficient improvements to buildings owned by tax-exempt organizations, government entities, or Indian tribal governments, the deduction can be allocated to the architect, engineer, or contractor who designed the energy-efficient features. The allocation is made through a written agreement between the building owner and the designer, signed before the deduction is claimed.
What buildings qualify for Section 179D?
Section 179D applies to commercial buildings (commercial, industrial, retail) and residential rental buildings of 4+ stories. It also applies to government-owned buildings (federal, state, local) and buildings owned by Indian tribal governments and tax-exempt organizations — with the deduction allocated to the building's designer for these entities. Single-family homes and low-rise multifamily buildings are not eligible (see Section 45L instead).
What energy efficiency improvements qualify?
Three building systems are eligible for partial deductions: (1) Interior lighting systems (up to $0.50-$5.00/sq ft for the lighting portion alone if it meets 25% energy reduction vs. ASHRAE 2007 baseline); (2) HVAC and hot water systems (up to $0.50-$5.00/sq ft for the HVAC portion); (3) Building envelope (up to $0.50-$5.00/sq ft for the envelope portion). The full deduction applies when all three systems together achieve the required percentage energy reduction vs. the baseline.
How is the 179D deduction certified?
The energy efficiency must be certified by a qualified individual: an independent licensed engineer or contractor (not the same entity claiming the deduction) who uses IRS-approved energy modeling software to demonstrate the energy savings versus the ASHRAE 90.1-2007 reference building. The certification report, along with all supporting calculations and the software output, must be retained by the taxpayer. The IRS does not require pre-approval but will request this documentation in an audit.
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