The Section 179D Energy Efficient Commercial Buildings Deduction rewards energy-efficient commercial buildings with a federal tax deduction — and the only way to claim it is through a qualified energy model and certification. For owners and designers, it can turn efficiency investments into a meaningful tax benefit.
What 179D is worth
Post-Inflation-Reduction-Act, 179D uses a sliding scale that for 2025 ranges from roughly $0.58 to $5.81 per square foot (the figures are inflation-indexed each year):
- Without prevailing-wage & apprenticeship (PWA): from about $0.58/sq ft at 25% savings up to a cap near $1.16/sq ft.
- With PWA compliance: from about $2.50/sq ft at 25% savings, rising with each extra percentage point of savings to roughly $5.00+/sq ft.
On a large building, that can total hundreds of thousands of dollars.
The 25% energy-savings threshold
To qualify, the building must demonstrate at least 25% energy savings versus the applicable ASHRAE 90.1 reference standard, through improvements to the envelope, HVAC, service hot water and/or interior lighting. The more the design beats 25%, the larger the deduction — which is exactly what an energy model quantifies.
What's required to claim it
179D has two technical pillars:
- Energy modeling in IRS/DOE-qualified software, comparing the building to the reference standard to establish the savings percentage.
- Certification by a qualified individual (a licensed PE or contractor) including a site visit, confirming the modeled measures were installed.
For government and other tax-exempt buildings, the deduction can be allocated to the designer (architect or engineer) — a valuable benefit many design firms overlook.
An important deadline
Recent legislation set a sunset for 179D: it does not apply to property whose construction begins after June 30, 2026. Projects already underway should evaluate their eligibility now rather than later.
The takeaway
179D rewards efficiency that's already common in good design — but it only converts to dollars if the savings are properly modeled and certified. If you have efficient commercial projects in the pipeline, an early modeling check tells you whether they qualify and how large the deduction could be.
Want to check a project's 179D eligibility?
We run the energy modeling that establishes 179D savings against ASHRAE 90.1 and support the certification process. Let's talk about your buildings.
Get in touchThis article is general guidance, not tax advice. 179D amounts, reference standards and deadlines change — always confirm current requirements with the IRS and a qualified tax professional for your specific project.