IRS Releases Notice to Restrict Renewable Energy Methods

Editor’s note: This article is for informational and editorial purposes only. Renewable energy tax credit planning should be reviewed with a qualified tax professional, because the IRS does not hand out “oops, my bad” coupons.

Introduction: A Small IRS Notice With a Very Large Shadow

The IRS has released Notice 2025-42, and for renewable energy developers, tax equity investors, utilities, and project finance teams, it is not exactly beach reading. The notice changes how many wind and solar projects can prove they have “begun construction” for purposes of federal clean electricity tax credits. That phrase may sound like something only a tax lawyer could love, but it matters because it can determine whether a project qualifies for major federal incentives under Internal Revenue Code Sections 45Y and 48E.

In plain English, the IRS is making it harder for most wind and utility-scale solar projects to rely on paperwork and spending alone. Under prior guidance, developers often had two main routes to establish the beginning of construction: start significant physical work, or satisfy the famous “5% safe harbor” by paying or incurring at least 5% of total project costs and continuing to advance the project. Notice 2025-42 sharply narrows that second route for wind and most solar facilities. The new message is simple: show real physical work, not just a checkbook with ambition.

The notice lands in the wake of the One Big Beautiful Bill Act and Executive Order 14315, both of which pushed federal agencies to tighten the rules around wind and solar tax credits. As a result, renewable energy developers now face a compressed timeline, stricter documentation demands, and a more practical question: Has the project actually started, or has everyone merely attended twelve meetings, ordered coffee, and updated a spreadsheet?

What IRS Notice 2025-42 Actually Does

IRS Notice 2025-42 focuses on the “beginning of construction” rules for applicable wind and solar facilities seeking the clean electricity production credit under Section 45Y or the clean electricity investment credit under Section 48E. These credits are central to renewable energy finance because they can materially reduce project costs and improve investor returns.

The notice states that, for most wind and solar projects, the Physical Work Test is now the main method for proving construction began before the critical deadline. Except for certain low-output solar facilities, the 5% Safe Harbor is no longer available for this specific purpose if construction did not begin under prior rules before September 2, 2025.

That is the headline. The fine print is where things get spicy, in the same way hot sauce on your tax return would be spicy. The IRS did not eliminate every familiar rule. It retained the idea that both on-site and off-site physical work can count. It preserved a continuity safe harbor. It also kept exceptions for disruptions outside a taxpayer’s control. But it changed the planning playbook by pushing developers away from “we spent money” and toward “we started building something meaningful.”

Why the Beginning of Construction Rule Matters

The beginning of construction date matters because the OBBBA accelerated the phaseout of certain wind and solar credits. In general, wind and solar projects that begin construction after July 4, 2026, and are placed in service after December 31, 2027, face losing eligibility for the Section 45Y and 48E credits. Projects that establish construction before the deadline may have more runway, including the familiar four-year continuity safe harbor if they are placed in service within the required window.

For a developer, this is not just a tax footnote. It can affect whether a project secures financing, whether a power purchase agreement remains economically workable, whether tax equity investors stay at the table, and whether procurement teams need to move faster than a squirrel crossing a four-lane highway.

Tax credits often sit inside the financial model like structural beams. Remove them, and the project may still stand, but it might suddenly look expensive, wobbly, or unattractive to capital providers. That is why Notice 2025-42 has drawn so much attention from renewable energy lawyers, accountants, project sponsors, contractors, utilities, and investors.

The Big Change: Goodbye 5% Safe Harbor for Most Wind and Solar

Before Notice 2025-42, many developers relied on the 5% Safe Harbor because it provided a relatively clear financial test. If a taxpayer paid or incurred at least 5% of total project costs and then made continuous efforts to complete the project, construction could be treated as having begun. This was especially useful for large projects with long permitting, interconnection, procurement, and financing timelines.

Notice 2025-42 changes that for all wind projects and most solar projects. For those projects, simply incurring 5% of costs will generally not be enough to establish the beginning of construction for the OBBBA wind and solar credit termination rules. Instead, developers must rely on the Physical Work Test.

There is one important exception: low-output solar facilities with maximum net output of not greater than 1.5 megawatts AC may still use the 5% Safe Harbor. That matters for some distributed generation, community solar, behind-the-meter, and smaller commercial solar projects. However, the notice includes aggregation concepts for integrated operations, meaning developers should be careful about assuming that several small solar facilities can be sliced like pizza and treated separately if they are economically and operationally connected.

What Counts as Physical Work?

The Physical Work Test looks at the nature of the work, not merely the cost or volume of work. There is no fixed minimum dollar amount or percentage threshold. That can be helpful because a relatively small amount of significant work may count. It can also be nerve-racking because “facts and circumstances” is tax-speak for “please save every document and prepare for questions.”

Examples for Wind Projects

For wind facilities, on-site physical work may include excavation for foundations, setting anchor bolts into the ground, or pouring concrete foundation pads. Off-site work may also count if components such as turbines or tower units are manufactured under a binding written contract and are not simply pulled from a manufacturer’s existing inventory.

Examples for Solar Projects

For solar facilities, qualifying on-site physical work may include installing racks or other structures used to affix photovoltaic panels, collectors, or solar cells. Off-site manufacturing of important components such as mounting equipment, support structures, inverters, transformers, and power conditioning equipment may also count when the contractual and inventory rules are satisfied.

What Does Not Count

Notice 2025-42 is also clear about what does not qualify. Preliminary activities generally do not count as physical work of a significant nature. That includes planning, designing, securing financing, researching, conducting mapping or modeling, obtaining permits and licenses, environmental and engineering studies, site clearing, and certain forms of test drilling or land contouring.

This is where the notice becomes especially practical. A developer may have spent months and millions preparing a project, but if the activity is still preliminary, it may not establish beginning of construction. In other words, a beautiful binder full of permits may impress your lender, but it may not impress the Physical Work Test.

The Continuity Requirement: Starting Is Not Enough

Beginning construction is only part of the story. A taxpayer must also maintain a continuous program of construction. Notice 2025-42 keeps a continuity safe harbor: if a project is placed in service by the end of a calendar year that is no more than four calendar years after the year construction began, the project is generally treated as satisfying the continuity requirement.

If the project falls outside that safe harbor, the facts and circumstances become more important. The IRS also recognizes certain excusable disruptions, including severe weather, natural disasters, permitting delays, interconnection-related delays, labor stoppages, shortages of specialized equipment, endangered species issues, financing delays, and supply shortages. That list is welcome because renewable projects often encounter delays that are nobody’s idea of a good time.

Still, developers should not treat the continuity rules casually. A project that begins qualifying physical work and then naps for two years may have a problem. The IRS wants evidence that construction is moving forward, not just evidence that someone once poured concrete and then disappeared like a contractor in a sitcom.

Who Is Most Affected?

The biggest impact falls on utility-scale wind and solar developers that expected to rely on the 5% Safe Harbor after September 2, 2025. These projects now need to demonstrate significant physical work before the deadline if they want to preserve credit eligibility beyond the accelerated placed-in-service rules.

Tax equity investors are also affected. Investors typically demand strong documentation before pricing tax benefits into a deal. After Notice 2025-42, they may ask harder questions about contracts, equipment manufacturing, construction logs, invoices, delivery records, site photos, engineering reports, and legal opinions. In short, the tax credit file is going to need more than a cheerful PDF named “final_final_REALfinal.pdf.”

Small solar developers may benefit from the low-output solar exception, but they still need to be cautious. A 1.5 MW AC threshold sounds simple until multiple facilities share ownership, interconnection, timing, or end users. Developers should analyze whether projects are treated as integrated operations and whether aggregation could push them outside the low-output exception.

Practical Compliance Steps for Renewable Developers

First, developers should review every project schedule against the relevant dates: September 2, 2025, July 5, 2026, and December 31, 2027. These dates now shape tax strategy, procurement sequencing, construction planning, and financing discussions.

Second, project teams should identify what specific physical work can begin and how it will be documented. For wind, that might involve foundation work or custom component manufacturing. For solar, that may involve rack installation or qualifying off-site manufacturing under binding written contracts. The key is to connect each activity to the actual facility and preserve evidence that the work is significant and not merely preliminary.

Third, contracts should be reviewed carefully. Off-site work performed by third parties can count only when it is tied to binding written contracts and not simply to ordinary inventory items. That means procurement teams and legal teams need to coordinate early. Tax planning should not be introduced after the purchase order is already lost in someone’s inbox.

Fourth, developers should build a documentation package while the project is happening, not after the IRS asks questions. Construction logs, photos, dated invoices, supplier certifications, work orders, engineering memos, and board approvals can all become important. A tax credit file should tell a coherent story: what work began, when it began, why it was significant, who performed it, and how construction continued.

Why the Notice Is Controversial

Supporters of the policy argue that the IRS is enforcing congressional intent and preventing developers from using broad safe harbors to preserve credits for projects that have not meaningfully started. From that perspective, the notice is a guardrail against artificial acceleration.

Critics argue that the guidance injects uncertainty into an industry already facing long interconnection queues, supply chain volatility, local permitting disputes, and shifting federal policy. They warn that stricter rules could slow renewable energy deployment, raise project costs, and make financing more difficult. Developers may now rush to prioritize projects that can physically start sooner, even if other projects might be more valuable to the grid in the long run.

Both sides can agree on at least one thing: Notice 2025-42 makes timing and documentation more important. The renewable energy industry has always had engineering challenges. Now it has an even bigger calendar challenge.

Specific Example: A Solar Project Under the New Rules

Imagine a developer planning a 100 MW solar project. Before the notice, the developer might have tried to establish beginning of construction by incurring 5% of total costs through equipment purchases or other eligible expenditures, then continuing development efforts. Under Notice 2025-42, if the project did not begin construction under prior rules before September 2, 2025, that financial safe harbor generally will not work.

The developer would instead need to begin physical work of a significant nature before the deadline. Installing racks at the project site may help. Off-site manufacturing of project-specific mounting structures or inverters may also help if done under the right contract and not from normal inventory. But site clearing, design work, financing negotiations, permit applications, and environmental studies would not be enough by themselves.

That difference can change project sequencing. A developer may need to lock in engineering decisions sooner, execute binding contracts earlier, coordinate with suppliers more tightly, and gather evidence from the field in real time. The tax department, construction manager, and procurement team can no longer operate like separate planets.

Specific Example: A Small Solar Facility

Now imagine a 1 MW AC commercial solar facility installed behind a customer’s meter. Because the facility is not greater than 1.5 MW AC, it may qualify as a low-output solar facility and may still be able to use the 5% Safe Harbor. That is a meaningful exception for smaller projects.

However, the developer should still analyze whether the facility is part of integrated operations with other solar facilities. If multiple projects are owned by the same or related taxpayers, placed in service in the same taxable year, and connected through the same point of interconnection or supporting the same behind-the-meter end user, the IRS may measure them together for the 1.5 MW threshold. In short, the “small project” exception is helpful, but it is not a magic invisibility cloak.

Experience Notes: What This Looks Like in the Real World

In practical project development, rules like Notice 2025-42 rarely stay confined to the tax department. They move through the entire organization. The first people to feel the pressure are usually development managers, because they must convert a legal standard into a construction schedule. A phrase like “physical work of a significant nature” becomes a calendar meeting, a supplier call, a site visit, a revised budget, and possibly a slightly tense conversation with the CFO.

A common experience in renewable energy planning is that everyone agrees deadlines matter until the deadline starts driving decisions. Then the developer must choose which projects are mature enough to advance. A wind project with land control, interconnection progress, turbine supply options, and local support may jump to the front of the line. A solar project still waiting on permits may be paused, even if it has excellent economics on paper. Notice 2025-42 increases the value of shovel-ready projects and reduces the value of “almost ready” projects. Unfortunately, “almost ready” is where many infrastructure projects live, unpack their boxes, and stay for a while.

Another real-world lesson is that documentation must be designed before work begins. Project teams often assume they can reconstruct a record later. That is risky. If a manufacturer begins producing project-specific components, the developer should preserve the contract, manufacturing schedule, production records, invoices, photos if available, and evidence that the components are not ordinary inventory. If a contractor begins foundation excavation or rack installation, the project file should include dated field reports, site photos, survey references, and payment records. The goal is to make the evidence boring, complete, and easy to follow. In tax controversy, boring is beautiful.

Financing teams will also feel the change. Tax equity investors dislike uncertainty the way cats dislike baths. If the beginning of construction position is weak, investors may demand stronger indemnities, discount the value of credits, delay closing, or walk away. That means developers should not treat Notice 2025-42 as a compliance memo only. It is also a financing issue, a procurement issue, and a board-level risk management issue.

There is also a human side. Renewable energy teams have spent years adapting to tariffs, supply shortages, interconnection delays, local opposition, evolving domestic content rules, and changing federal incentives. Notice 2025-42 adds another layer. The most successful teams will be those that respond with discipline instead of panic. They will map deadlines, rank projects, secure contracts, begin qualifying work where feasible, document everything, and communicate clearly with investors and customers. The least successful teams will rely on assumptions, vibes, and a heroic spreadsheet last updated by someone who left the company in March.

Conclusion: Renewable Energy Tax Planning Just Got More Physical

IRS Notice 2025-42 does not end renewable energy development in the United States, but it does make the path narrower for many wind and solar projects seeking federal clean electricity tax credits. The notice shifts the emphasis from financial commitment to physical progress. For most wind and utility-scale solar facilities, the 5% Safe Harbor is no longer the easy doorway it once was. Developers now need real construction activity, strong contracts, continuous progress, and disciplined records.

The biggest takeaway is not simply “start early.” It is “start correctly.” A project must begin the right kind of work, at the right time, with the right documents, and with a credible plan to keep moving. In renewable energy, sunshine and wind may be free, but tax credit eligibility definitely is not.