Section 179D has long provided a federal tax incentive for investments in energy-efficient commercial buildings. By linking tax savings to measurable improvements in building performance, the Energy Efficient Commercial Buildings Deduction created an opportunity for qualifying building owners and, in certain circumstances, designers to recover some of the costs of energy-efficient construction and improvements.
The deduction is now entering a new phase. Under the One Big Beautiful Bill Act, Section 179D does not apply to property for which construction begins after June 30, 2026. However, qualifying property with construction that began on or before that date can remain eligible, so organizations with ongoing projects should understand how the deduction works and what is required to claim it.
The purpose of Section 179D
Section 179D was designed to encourage greater energy efficiency in commercial buildings by providing a deduction for qualifying improvements to key building systems. The incentive applies to eligible property installed as part of new construction or building upgrade projects.
Rather than rewarding the purchase of a particular product or technology, Section 179D focuses on a building’s energy performance. Qualifying projects must demonstrate that eligible improvements achieve the energy savings required under the applicable rules.
The deduction can therefore provide a financial benefit alongside the operational benefits that may come from energy-efficiency investments.
Building systems covered by Section 179D
Section 179D applies to energy-efficient property installed as part of specific commercial building systems. Eligible improvements can involve:
- Interior lighting systems
- Heating, ventilation, and air conditioning (HVAC) systems
- Hot water systems
- The building envelope
Other energy-consuming equipment and processes generally do not qualify simply because they reduce overall energy use. Improvements must fall within the building systems covered by Section 179D and meet the applicable energy-performance requirements.
Both new construction and renovations can potentially qualify. This makes the deduction relevant not only when developing a new commercial building but also when making substantial energy-efficiency improvements to an existing property.
Two pathways for demonstrating energy savings
For qualifying property placed in service in 2023 and later, there are two primary pathways for pursuing a Section 179D deduction.
The Traditional, or Modeling, Pathway can apply to both new construction and building upgrades. Energy modeling compares the building’s expected performance with a reference building and determines whether the project achieves the required reduction in annual energy and power costs.
The Alternative, or Measurement, Pathway applies to qualifying retrofit projects. Rather than relying on modeled performance, it uses measured energy use before and after the improvements to establish savings. The building must have originally been placed in service at least five years before the qualified retrofit plan is established.
The appropriate pathway therefore depends on the project’s nature and timing, as well as the information available to demonstrate its performance.
Energy savings determine the available deduction
For property placed in service in 2023 and later, a project generally must achieve at least a 25% reduction under the applicable energy-savings methodology to qualify. The deduction available per square foot increases as the project’s energy savings improve.
The exact dollar amounts are adjusted for inflation, making the property’s placed-in-service year important when determining the available benefit.
For tax years beginning in 2026, for example, IRS instructions provide a base deduction starting at $0.59 per square foot for 25% energy savings, increasing as additional energy savings are achieved. The maximum base amount is $1.19 per square foot at the applicable maximum savings threshold.
The deduction is also limited by the cost of the qualifying installed property, so calculating the potential benefit requires more than simply multiplying a building’s total square footage by a single rate.
Prevailing wage and apprenticeship requirements can increase the value
Section 179D can provide a substantially larger deduction when applicable prevailing wage and registered apprenticeship requirements are satisfied.
For qualifying projects, meeting these requirements can increase the applicable per-square-foot deduction by approximately five times the base amount.
Because this difference can materially affect the available deduction, organizations should consider labor requirements and associated documentation as part of their Section 179D planning rather than evaluating them only after construction has been completed.
Eligibility extends beyond commercial building owners
Commercial building owners are among the primary taxpayers eligible to claim Section 179D, but the deduction is not limited to them.
Beginning in 2023, designers of qualifying energy-efficient property installed in buildings owned by specified tax-exempt entities can also potentially receive an allocation of the deduction. Eligible entities include certain government entities, Indian tribal governments, Alaska Native Corporations, and organizations exempt from tax under Chapter 1 of the Internal Revenue Code.
For these projects, the eligible building owner does not directly benefit from a federal income tax deduction. Instead, the deduction can be allocated to an eligible designer who creates the property’s energy-efficient systems.
This allocation process introduces additional requirements, making proper documentation important for both the entity allocating the deduction and the designer claiming it.
Certification and documentation support the claim
A qualifying project requires more than demonstrating that energy-efficient equipment was installed.
Section 179D includes certification requirements intended to establish that the property meets the applicable energy-savings standards. For projects using the Traditional Pathway, qualified individuals certify the energy-efficiency impact of the eligible property placed in service. Energy modeling and inspection therefore play important roles in supporting the deduction.
Project documentation may include building plans, energy models, specifications, construction records, cost information, certification materials, and, where applicable, allocation documentation.
Taxpayers claiming qualifying property placed in service during the tax year use Form 7205 to calculate and claim the deduction and provide information concerning the building, certification, and any applicable allocation.
Keeping these records throughout a project can make the eventual tax analysis much more efficient than trying to reconstruct the necessary information after completion.
The June 30, 2026 termination changes future planning
The One Big Beautiful Bill Act terminated Section 179D for property whose construction begins after June 30, 2026. Importantly, the law uses the beginning of construction as the cutoff rather than requiring all qualifying property to be placed in service by June 30.
As a result, Section 179D remains relevant after the termination date for qualifying projects that began construction on or before June 30, 2026. The property’s placed-in-service date remains important for determining the applicable deduction amounts and other program rules.
Organizations with ongoing construction or renovation projects should therefore avoid assuming that the deduction is no longer available simply because a project extends beyond June 2026.
Instead, focus on when construction began, whether the property meets the applicable energy-efficiency requirements, and what documentation is needed to support the eventual claim.
Capturing the remaining value of Section 179D
Section 179D connects investments in commercial building efficiency with a potentially significant federal tax deduction. Determining the available benefit requires evaluating the qualifying building systems, measuring energy savings, identifying the appropriate compliance pathway, considering prevailing wage and apprenticeship requirements, and completing the required certification and documentation.
The June 30, 2026 termination makes that analysis particularly important for projects already in progress. Qualifying projects that began construction by the deadline may continue to present Section 179D opportunities even when the property is placed in service later.
Ayming helps organizations evaluate eligible projects, complete the technical analysis required for Section 179D, and develop the documentation necessary to support a claim. For organizations with projects that began construction before the cutoff, reviewing eligibility now can help ensure they don’t overlook available deductions.
Speak with an energy incentives expert to evaluate your Section 179D opportunities.
