179D Energy Efficient Commercial Buildings Deduction
Up to $2.50 per sq ft for energy-efficient commercial buildings.
The §179D deduction rewards owners and designers of commercial buildings that reduce energy use through efficient HVAC, lighting, building envelope, and hot water systems. Unlike a credit, it is a deduction — but for large buildings it can produce six-figure tax savings in a single year.
How it works
179D is the federal Energy Efficient Commercial Buildings Deduction. It applies to buildings that are designed to reduce annual energy and power costs by at least 25% compared to a reference standard, and the deduction scales with the percentage of energy cost reduction up to a current maximum of $2.50 per square foot.
The base deduction is available to the building owner. For government-owned buildings, the deduction can be allocated to the designer — typically the architect, engineer, or contractor responsible for the energy-efficient property. This makes 179D valuable for both private owners and public-sector design teams.
To qualify, a project must be certified by a qualified professional using approved energy modeling software. The building must be placed in service, and the certification must be completed before the deduction is claimed. The deduction can be claimed on the current-year return or, for certain prior-year projects, through an amended return.
You may qualify if
- You own or designed a commercial building with efficient systems
- The building reduces energy costs by at least 25% vs. ASHRAE baseline
- The building is at least 50,000 sq ft or has significant energy use
- You have a qualified professional who can certify the energy model
What the engagement looks like
01
Fit check
Intake covers building size, type, systems, placed-in-service date, and ownership status.
02
Energy model
A qualified professional models the building against the ASHRAE 90.1 baseline to measure energy cost savings.
03
Certification
The model is reviewed and certified to support the §179D deduction amount.
04
Claim
Your CPA claims the deduction on the return — or, for government projects, the allocation is passed to the designer.
Case study
Regional office building owner
Office · Southeast
Situation
A 120,000 sq ft office building completed a major HVAC and lighting retrofit in 2024. The owner’s CPA had treated the project as a routine capital improvement and had not claimed the §179D deduction, leaving significant tax savings unclaimed.
Approach
The specialist engaged a qualified energy modeler to compare the retrofitted building against the ASHRAE 90.1 baseline. The modeling showed a 35% energy cost reduction, qualifying the project for the maximum §179D deduction available under current law.
Result
Claimed a deduction of $2.50 per sq ft across 120,000 sq ft, producing a $300,000 deduction. At a 37% federal tax rate, the deduction saved the owner roughly $111,000 in federal tax. The study fee was 8% of the deduction value.
Building sq ft
120,000
§179D deduction
$300,000
Est. federal tax savings (37%)
$111,000
Study fee (8% of deduction)
$24,000
Illustrative example based on typical engagement outcomes. Actual results depend on your specific facts.
Common questions
Can I claim 179D on a building I designed but do not own?
Yes, for government-owned buildings the owner can allocate the deduction to the designer. For privately owned buildings, the owner generally claims the deduction. The rules are specific, so the specialist confirms the correct party before certification.
Does the deduction require prevailing wage or apprenticeship?
The base deduction does not require prevailing wage or apprenticeship, but projects that meet those requirements may qualify for a higher deduction. The specialist helps you model which path is more advantageous for your project.
Can I claim 179D and 45L on the same project?
Often yes. A mixed-use project with residential units and commercial space can potentially claim 45L on the dwelling units and 179D on the commercial building. The specialist structures the energy modeling to maximize both benefits.
Ready to see if this fits?
Short intake, no cost, matched with a specialist within days.