You’d think by now the question of what actually qualifies as Section 48 eligible energy property would be pretty well settled. On paper, it mostly is. In the real world of diligence calls and buyer objections, developers and corporate tax teams still trip over the same eligibility boundaries and cost basis questions.
Here’s the thing. The credit covers projects that began construction before 2025. A substantial chunk of commercial solar and storage credits moving through the transferable market right now were generated under these rules. Buyers need to know what qualifies.
Getting the eligible property classification wrong doesn’t trim your credit. It kills it entirely.
Table of Contents
What the IRA Added to the Technology List
Before the IRA, Section 48 covered solar PV, concentrated solar, geothermal, fuel cells, microturbines, combined heat and power, small wind, and waste energy recovery. Decent list, but not exactly expansive.
The IRA changed that in some pretty meaningful ways. Standalone energy storage became eligible for the first time. Previously, batteries only got the credit when physically paired with a generating asset like solar. That exclusion kept storage developers completely out of the ITC market. Once the door opened, developers shifted billions in pipeline toward these structures almost overnight.
Qualified biogas property got added too. So did microgrid controllers. And here’s one that flies under the radar: qualified interconnection property for smaller projects, which had always been treated as non-qualifying capex, finally became eligible.
On smaller commercial solar installs, interconnection can eat up a real share of total spend. Pulling those costs into the eligible basis expanded the credit’s reach on exactly the project profiles that needed help the most.
The Cost Basis Math That Makes or Breaks the Credit
The Section 48 credit gets calculated as a percentage of eligible cost basis for qualifying energy property placed in service during the tax year. The Base rate is 6%. Meet prevailing wage and apprenticeship requirements, and you jump to 30%.
Layer on the domestic content bonus and energy community bonus, and you’re looking at an effective credit north of 50%. Low-income community adders can push it further, though those are allocated competitively.
Now here’s where things go sideways. The credit runs on eligible basis. Not total project cost. Equipment, installation labor, certain owner’s costs, and qualified interconnection expenses count. Land doesn’t. Financing fees don’t. Most soft costs get stripped out.
Developers who stuff too much into the basis create recapture exposure that buyers sniff out during diligence and price against hard. Developers who undercount eligible costs leave real credit value uncollected. The basis calculation is where most project-level value gets won or lost.
The Structural Edge of Legacy Credits
Here’s something sharp buyers have been quietly leveraging.
Legacy credits from projects that broke ground before 2025 aren’t subject to any Prohibited Foreign Entity restrictions the OBBBA placed on Section 48E. No FEOC material assistance test. No MACR threshold. No supply chain verification against PFE-sourced components. None of it.
That creates a genuine two-tier dynamic. Pre-2025 credits come with simpler diligence, faster closings, and zero FEOC compliance cost baked into the price.
For corporate buyers shopping through a clean energy tax credit marketplace, the difference isn’t academic. Legacy credits with clean documentation and verified bonus adders are sitting at the top of the pricing range, and the FEOC exemption is a big reason why.
What the Transition to 48E Means for Buyers
Projects that kicked off construction before 2025 can still elect to claim under legacy Section 48 rules even if the system went live in 2025 or 2026. Anything that started after falls under the newer framework automatically.
That election actually matters. Claiming under the legacy rules versus the new ones can produce meaningfully different credit outcomes depending on the technology, how cost basis shakes out, and whether the supply chain can clear FEOC compliance.
These credits will keep transacting through 2026 and into 2027 as pre-2025 projects hit commercial operation. That’s real supply. Buyers who understand the eligibility framework are the ones underwriting the cleanest deals.
Conclusion
Section 48 eligible energy property is a broader category than most corporate buyers expect, especially after the IRA bolted on standalone storage, biogas, microgrid controllers, and interconnection costs. But eligibility alone doesn’t get you the credit. The value lives in getting cost basis right, stacking adders with documentation that holds up under audit, and understanding where the legacy framework carries structural advantages over its successor.
For buyers, legacy credits are some of the lowest-risk inventory in the transferable market today. For developers bringing pre-2025 projects across the finish line, the basis calculation is where the money actually gets made.
Or quietly lost. Depends on how much attention you’re paying.
