Cost Seg vs Section 179D vs 45L: Three Tax Incentives Compared
Cost segregation, Section 179D, and Section 45L are three separate real estate tax incentives that can stack on the same property. Cost seg accelerates depreciation of existing basis. Section 179D allows a deduction up to $5 per square foot for energy-efficient commercial property. Section 45L provides a tax credit up to $5,000 per unit for energy-efficient new residential. All three are claimed independently.
Cost segregation
Accelerates depreciation of existing basis by reclassifying components from 27.5 or 39 year recovery to 5, 7, or 15 year recovery. Combined with 100% bonus depreciation under OBBBA, produces large first-year deductions.
Applies to virtually all income-producing real estate. Fee: $795 to $2,995+. ROI typically 10x or higher on properties above $500K basis.
Section 179D
Section 179D allows a deduction up to $5 per square foot for energy-efficient commercial buildings and government buildings. Updated significantly by the Inflation Reduction Act of 2022 with prevailing-wage and apprenticeship requirements for the full benefit.
Applies primarily to commercial buildings (offices, warehouses, retail) and government buildings. Government-building designers can claim the deduction even though they do not own the property.
Section 45L
Section 45L provides a tax credit up to $5,000 per qualified energy-efficient residential unit. Applies to new construction and substantial rehabilitation of multifamily and single-family residential property meeting Energy Star or Zero Energy Ready standards.
Eligible builders, developers, and owners claim the credit on Form 8908. Combined with cost segregation on the same property, the credit and the accelerated depreciation stack.
Stacking strategy
Most projects can claim all three: cost seg on the property's overall basis, Section 179D on the qualifying commercial portion, Section 45L on the qualifying residential units. Each is claimed independently with its own engineering or certification work.
WeCostSeg specializes in cost seg. Section 179D and 45L typically require energy engineering specialists. The deliverables are independent but the taxpayer combines them on the return.
Frequently asked questions
- How does WeCostSeg coordinate with my CPA?
- Every engagement follows the three-touch CPA Coordination Protocol. Preliminary analysis CC'd to your CPA on intake, draft report shared five business days before final delivery, and Form 3115 filing coordinated when a Section 481(a) adjustment applies.
- Does OBBBA's 100% bonus apply to my acquisition?
- 100% applies to property under a binding contract on or after January 20, 2025 per Public Law 119-21. Property under a binding contract on or before January 19, 2025 stays on the legacy phase-down: 40% in 2025, 20% in 2026, 0% in 2027 and after.
- Is audit defense included?
- Yes. Every WeCostSeg engagement includes five years of written audit defense at no extra charge, aligned to the 13 Principal Elements of a Quality Cost Segregation Study under IRS Publication 5653 Chapter 4.
- Can I get a free preliminary analysis?
- Yes. Submit property details via the free proposal form or WhatsApp. Engineer-reviewed estimate returned within four business hours during US Eastern hours.
Zawwad Ul Sami, Founder
Zawwad Ul Sami is the founder of WeCostSeg, a founder-led cost segregation firm serving real estate investors across the US. He focuses on strategy, pricing, and the firm's overall direction.