The Domestic Content Bonus in 2026: How Commercial Solar Reaches 40%

Solar CCS ·

Section 48E pays commercial solar 30%, plus 10 points for domestic content. In 2026 the bar is 50% — and a new foreign-entity test can disqualify a project that clears it.

If you own a business in Southern California and you are looking at solar, there is one number that decides whether your project returns 30% or 40% of its cost as a federal tax credit. That number is your domestic content percentage. In 2026 the bar moved to 50%, and a separate new rule can disqualify a project that clears it.

This is the commercial owner's version of the domestic content bonus. No homeowner guidance, no expired credits, just the math that applies to a Section 48E project starting today.

One thing to get out of the way first: the 30% residential credit under Section 25D ended for expenditures after December 31, 2025. If you are a homeowner buying a system with cash or a loan, there is no federal credit for you. Everything below is about business-owned commercial projects under Section 48E.

The bonus is 10 percentage points, not 10 percent

Section 48E, the Clean Electricity Investment Credit, is the credit that survived. It is a percentage of your total eligible project cost, claimed in the year the system is placed in service.

The stack works like this:

A 10-point bonus on a $1,200,000 project is $120,000. It is not a rebate and it is not a deduction. It is a dollar-for-dollar reduction of federal tax liability, and it stacks on top of MACRS depreciation.

The 1 MW line is the most important number in commercial solar

Most business owners do not realize how much rides on staying under 1 megawatt.

Under the Treasury regulations, a project gets the full 30% applicable percentage if it meets any one of three conditions: maximum net output under 1 MW AC, construction began before January 29, 2023, or the project satisfies prevailing wage and apprenticeship requirements (26 CFR 1.48E-3). Miss all three and the credit drops toward the 6% base rate, and the domestic content bonus shrinks from 10 points to 2 (IRS domestic content bonus credit).

Here is the part that matters. That 1 MW is measured in alternating current. For a DC system, the regulation says you take the lesser of the summed DC nameplate capacity or the nameplate capacity of the inverter that converts DC to AC (26 CFR 1.48E-3).

In practice, a 1.2 MW DC array paired with 990 kW of inverter capacity is under the 1 MW line. You keep the full 30%, you get the full 10-point domestic content bonus, and you never touch prevailing wage or apprenticeship paperwork. On a warehouse roof that difference can be worth six figures and months of compliance administration.

There is a real tradeoff here, and it should be priced rather than assumed. A DC-to-AC ratio that high clips output during peak production hours, so you give up some annual kilowatt-hours in exchange for the tax treatment. On most commercial rooftops the credit is worth more than the clipped energy, but that is a calculation to run against your building's actual load profile. It is not a rule of thumb.

If your load genuinely needs more than 1 MW AC, prevailing wage and apprenticeship compliance is usually still worth it. It just has to be planned from day one, not discovered at closing.

In 2026 the threshold is 50%

The Inflation Reduction Act originally fixed the investment credit's domestic content threshold at 40% regardless of when construction started. The One Big Beautiful Bill Act corrected what was widely treated as a drafting error and put the investment credit on the same escalating schedule as the production credit (Stoel Rives).

Source: Eide Bailly, SolarEdge

Two things follow. A project starting construction this year needs 50%. A project that slips into 2027 needs 55%. That five-point step is enough to change equipment selection, so the year you break ground belongs in the conversation early.

How the 50% is actually calculated

You do not need to interrogate every supplier for direct cost data. The IRS publishes an elective safe harbor with pre-assigned cost percentages for each component of a solar project, developed with the Department of Energy. You add up the percentages for the components that are US-produced and compare the total against your threshold.

The current table is in Notice 2025-08, which modified the original 2024 safe harbor with updated cost percentages and finer project categories (Orrick). It splits solar into separate tables for rooftop and ground-mount, and it added a second set of percentages for modules built with domestic crystalline silicon cells made from domestic wafers.

Here are the numbers for a commercial rooftop system with a string inverter, which describes most warehouse and retail projects:

Source: IRS Notice 2025-08, Rooftop (String) table. Remaining smaller line items, including junction box, edge seals, pottants, bus ribbons, and bypass diodes, account for the balance to 100%.

Three observations that change how you buy equipment.

Cells are the whole ballgame. At 38.5% standard, the cell line is more than double the next largest item on the list, racking rails at 18.7%. At 52.1% with domestic wafers, it clears the entire 50% threshold by itself. No other sourcing decision on the project comes close to mattering this much.

Racking is the sleeper. Rails plus fasteners plus assembly is roughly 24.6% on a rooftop string system. US-made racking is widely available and rarely carries a meaningful premium. Very few buyers ask about it.

Microinverters change the math. On a module-level power electronics system, the cell percentage drops to 31.1% standard and 43.9% with domestic wafers, because the electronics absorb more of the project cost. Domestic cells alone will not clear 50% on an MLPE system. You need cells plus racking, or cells plus domestic microinverters.

You pick one column and use it for the entire project. You cannot mix the standard column for some components and the domestic-cell column for others.

Two scenarios on the same building

Say it is a 750 kW AC rooftop system on an Inland Empire distribution center, construction starting in 2026, so the threshold is 50%.

Scenario A. US-assembled modules, imported cells.

You get there, but only by domestically sourcing the module frame and the glass on top of everything else. Lose the glass and you are at 44.4% and the bonus is gone. This is a real risk on projects where the module is "made in America" in the assembly sense only.

Scenario B. Modules with US cells made from US wafers.

The cells clear the threshold on their own. Everything after that is margin against a supplier substitution or a documentation gap. If you are choosing between two otherwise comparable modules, the one with domestic cells and domestic wafers is worth a real premium, because it converts a fragile qualification into a durable one.

The new gate: foreign entity rules

This is the part most 2026 buyers have not caught up to, and it can undo everything above.

Separate from domestic content, the One Big Beautiful Bill Act added restrictions on receiving "material assistance" from a prohibited foreign entity. For Section 48E projects, these apply to any project beginning construction after December 31, 2025 (Bracewell).

You calculate a material assistance cost ratio: total direct costs minus costs attributable to prohibited foreign entities, divided by total direct costs. The result has to meet a floor that rises every year (Alvarez & Marsal).

Source: Alvarez & Marsal, Norton Rose Fulbright

Look hard at the storage column. A battery project starting construction in 2026 needs 55% non-prohibited content, materially harder than the 40% for solar, because of concentrated Chinese supply in cells and critical minerals (Alvarez & Marsal). If you are adding storage to a solar project, the storage carries its own separate test.

These are two different tests, and passing one does not mean passing the other. Domestic content asks whether a component was made in the United States. Material assistance asks whether a prohibited foreign entity was involved in making it. A module assembled in Texas from cells produced by a restricted-ownership supplier can help your domestic content number through its assembly and bill-of-materials lines while hurting your material assistance ratio. Both tests have to pass independently.

The IRS issued its first guidance on this in Notice 2026-15 on February 12, 2026. It provides three interim safe harbors: an Identification Safe Harbor letting you treat the existing domestic content tables as the complete list of components, a Cost Percentage Safe Harbor letting you use those same assigned cost percentages as your cost data, and a Certification Safe Harbor letting you rely on written certifications from your direct suppliers (Troutman Pepper).

That last one is the practical path for a commercial project. You are not auditing a factory in another country. You are collecting a written certification from the party you actually buy from. Treasury still owes purpose-built safe harbor tables for these rules by the end of 2026, so anything you do now runs against interim guidance (Norton Rose Fulbright).

Timing, and why this is urgent

The domestic content bonus is worth nothing if the underlying credit is gone.

Under the OBBBA, solar facilities whose construction begins after July 4, 2026 must be placed in service by December 31, 2027 to claim Section 48E at all (The Tax Adviser). That date has passed. A project starting construction today is on the accelerated clock.

What that means concretely:

  • If your project began construction on or before July 4, 2026, you are not subject to the 2027 placed-in-service deadline, though continuity requirements still apply.
  • If you are starting now, the entire project has to be designed, permitted, interconnected, built, and energized before the end of 2027. That is achievable for most commercial rooftop projects in the Inland Empire, but it is not a schedule with slack in it. Utility interconnection is usually the long pole, and it is the part you control least.
  • If you wait until 2027 to start, the domestic content threshold rises to 55% and the placed-in-service deadline gets very tight.

There is one live complication worth knowing about. The IRS guidance that governed how you prove construction began, Notice 2025-42, was vacated in full by the U.S. District Court for the District of Columbia on June 6, 2026 in Oregon Environmental Council v. IRS. The court found it arbitrary and capricious under the Administrative Procedure Act and declined to limit the ruling to the plaintiffs (McGuireWoods, Holland & Knight).

The effect is that the 5% safe harbor, incurring at least 5% of total project cost, is available again as a way to establish beginning of construction, alongside the physical work test. Notice 2025-42 had restricted most solar projects above 1.5 MW to the physical work test only (McGuireWoods).

Do not treat that as settled. The government is expected to appeal, an appellate reversal could apply retroactively, and the IRS can issue new guidance on remand (Holland & Knight). If your qualification strategy depends on the 5% safe harbor, that is a conversation for your tax counsel, not a blog post.

What this looks like on a Solar CCS commercial project

We build our three commercial tiers around domestically manufactured equipment, specifically so the bonus is reachable rather than theoretical. Every module, inverter, and storage product below is produced at a United States facility.

On the cell question specifically, SEG Solar announced a partnership with US cell manufacturer Talon PV to supply N-type cells starting in the first quarter of 2026, with the stated goal of reaching full made-in-America status for its modules (SEG Solar). SEG is also expanding Houston module capacity substantially (SEG Solar).

Three honest caveats, because this is where solar marketing usually overreaches.

First, we do not claim a specific percentage for your project until we have the supplier certifications in hand for the exact SKUs and production runs going on your roof. Domestic cell and wafer content varies by production batch. A module line that qualifies in the first quarter may not in the third. The certification is the asset, not the brand name.

Second, the safe harbor table's domestic-cell column is written around crystalline silicon cells and wafers. First Solar's Series 7 is cadmium telluride thin film, manufactured end to end in the United States. That is a strong domestic content position, but it does not map cleanly onto a table built for crystalline silicon, and your CPA needs to work the classification rather than assume the column applies.

Third, storage is a separate analysis from solar. US assembly of a battery system does not by itself answer the 55% material assistance test, because cells and critical minerals carry most of the cost and that supply chain is concentrated. If storage is part of your project, we treat its qualification as its own exercise and say so up front rather than folding it into the solar number.

The paperwork you will actually need

The bonus is claimed, not granted. You will need:

  1. A domestic content certification statement attached to Form 3468 with your return for the first tax year you claim the bonus (IRS).
  2. Supplier certifications for each component you are counting, tied to the specific SKUs and production periods on your project.
  3. Written direct-supplier certifications for the material assistance analysis, if you are using the Certification Safe Harbor under Notice 2026-15.
  4. Documentation of your construction start date and the method used to establish it.
  5. Prevailing wage and apprenticeship records, if the project is over 1 MW AC and you are relying on compliance rather than the One Megawatt Exception.

Keep all of it for the full recapture period. The credit can be recaptured, and the certification is what defends it.

What to do next

  1. Determine your AC size before anything else. Whether you land above or below 1 MW AC changes the base rate, the bonus size, and your labor compliance obligations. Inverter sizing is a design decision with a six-figure tax consequence.
  2. Get your construction start date on the calendar. The July 4, 2026 window has closed, so a project starting now needs to be energized by December 31, 2027. Work backward from interconnection.
  3. Ask every supplier two separate questions. Where was this made, and was any prohibited foreign entity involved in making it. Those are different questions with different answers.
  4. Price the domestic-cell option explicitly. On a rooftop string system it can carry the entire threshold by itself. Compare it against a stack that needs five other components to qualify.
  5. Bring your CPA in during design, not at tax time. Every meaningful decision here is made before equipment is ordered.

If you own a commercial building in Riverside, San Bernardino, or Orange County and want the actual numbers for your roof, we will model the credit stack alongside the install. We are a licensed California general contractor, CSLB #983330, and we handle commercial solar from 50 kW to 5 MW.

Request a commercial assessment or call (951) 706-5990.

Related reading: our Section 48E guide for commercial owners covers the underlying credit in more detail, Commercial Solar ROI in the Inland Empire walks through a full project payback, and Section 48E, Explained covers the basics of how the credit works.

This article is general information, not tax, legal, or financial advice. Federal energy tax credit rules changed substantially under Public Law 119-21 and remain subject to pending IRS guidance and active litigation. Thresholds, deadlines, and eligibility depend on your specific project, entity structure, tax position, and construction timeline. Consult a licensed CPA or tax attorney before making decisions based on any credit described here. Solar CCS does not provide tax advice.

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