The domestic content bonus adds real value to a solar project, but only if the sourcing math checks out before equipment gets ordered. For installers working on 48E-eligible commercial, TPO, or storage projects, the domestic content bonus can raise the investment tax credit by 2 or 10 percentage points depending on how the project qualifies. Getting there means understanding the solar domestic content requirements for 2026, the safe harbor Treasury built to simplify the calculation, and where domestic content stops and FEOC compliance starts.

This guide breaks down the 2026 domestic content bonus thresholds, walks through how the safe harbor calculation works, and gives you a practical checklist for procurement and documentation. It also explains how domestic content differs from FEOC compliance, since the two sourcing tests can apply to the same equipment but affect the tax credit in very different ways.

The solar domestic content bonus is an optional add-on to the Section 48E investment tax credit. A project that meets the domestic content requirement gets an extra 2 percentage points on the base credit rate, or 10 percentage points if the project also qualifies for the increased rate. That’s typically because it meets prevailing wage and apprenticeship requirements, has a net output under 1 megawatt, or began construction before January 29, 2023.

The requirement itself has two parts. Structural steel and iron products used in the project must be produced in the United States. Separately, a set percentage of the cost of manufactured products, like modules, inverters, and racking, must qualify as domestic content. That second number is the one that moves every year, and it’s the one most installers actually need to track.

This framework was first laid out in Notice 2023-38, which established the domestic content requirement, the recordkeeping rules, and the certification process taxpayers still rely on today.

• Optional bonus, not a requirement to claim the base 48E credit

• Adds 2 or 10 percentage points depending on the project’s credit rate

• Covers two separate tests: steel or iron, and manufactured products

• Thresholds are tied to the date construction begins, not the calendar year alone

• Certified by the taxpayer, not the installer, though installer records support that certification

For broader policy context on why the bonus exists, SEIA’s tax policy overview covers how it fits alongside the credit’s other adders, like the energy community bonus.

Domestic content and FEOC often get treated as two versions of the same sourcing test. They aren’t. Domestic content is optional and rewards U.S.-made equipment with a bigger credit. FEOC is mandatory, and it can eliminate the 48E credit entirely if a project pulls too much value from a prohibited foreign entity. A project can pass one test and fail the other.

Both tests apply to the same project, and a supplier’s equipment can affect either calculation independently. GreenLancer’s FEOC rules for solar installers guide covers the material assistance cost ratio in depth if you need the full PFE breakdown.

For §48E solar projects beginning construction in 2026, the manufactured products adjusted percentage is 50%. Projects beginning construction after December 31, 2026 are subject to a 55% threshold. The threshold depends on when a project begins construction, not simply the calendar year it happens to fall in, and Treasury’s current schedule has a mid-2025 break that catches a lot of people off guard.

The Steel or Iron Requirement applies to applicable project components that are classified as steel or iron products under the domestic content rules, and those products must be 100% produced in the United States regardless of when construction begins. This applies to items like structural steel and rebar, not to every steel part in the project. A steel bracket inside an inverter, for example, is generally evaluated under the manufactured products test instead.

The manufactured products threshold is the number that actually shifts your procurement decisions. According to the current Form 3468 instructions, the adjusted percentage for a §48E project is based on the beginning of construction date:

Offshore wind facilities follow a lower, separate schedule. For most solar and storage projects your team is designing today, the 50% threshold is the one that matters for anything breaking ground during 2026.

Calculating domestic content from scratch means collecting actual production costs from every supplier in the chain. Most manufacturers won’t share that information, which made the original rules nearly impossible to use in practice. Treasury’s elective safe harbor fixes that by letting taxpayers use standardized percentages instead.

The domestic content safe harbor started with Notice 2024-41, which assigned fixed cost percentages to individual components like modules, inverters, and racking. Notice 2025-08 updated those tables, splitting the solar PV category into separate ground-mount and rooftop tables and adding bonus percentages for projects using domestically produced cells and wafers. This is the version most installers should reference today.

Under the elective safe harbor, a project team identifies the manufactured products and manufactured product components listed in the applicable Notice 2025-08 table, applies the assigned cost percentages to whichever ones are domestically sourced, and compares the total against the required threshold.

Components not listed in the applicable table are left out of both sides of the calculation. Mixed-source situations and the optional domestic cell and wafer columns add extra nuance, so the exact table for your project type is worth reading closely rather than estimating.

Say a ground-mount tracking project begins construction in 2026, so it needs to clear the 50% manufactured products threshold. Under the Notice 2025-08 ground-mount tracking table, domestically produced solar cells are assigned 38.0%, frame or backrail hardware is assigned 6.0%, and torque tubes are assigned 11.0%. Sourcing all three domestically adds up to 55.0%, clearing the 2026 threshold before any other module, inverter, or tracker component gets counted.

• Confirm which safe harbor table applies: ground-mount, rooftop, or battery storage

• Pull the assigned cost percentage for each manufactured product component your project uses

• Add the percentages for every domestically sourced component

• Compare the total against the threshold tied to your beginning of construction date

Speccing equipment for an active bid? GreenLancer’s permit design and engineering documentation can reflect the exact make and model you plan to install, which makes it easier for the project owner to run this calculation accurately.

Not every component gets treated the same way, and the safe harbor tables split projects into three categories. Knowing which table applies to your project type keeps your procurement team from mixing up percentages that don’t actually apply.

• PV modules, including cells, frame or backrail, front glass, and encapsulant

• Inverters

• Trackers or fixed-tilt racking

• Structural steel piles, evaluated under the separate steel or iron requirement

• PV modules

• Module-level power electronics (MLPE) or string inverters, depending on system design

• Racking and mounting hardware

Battery energy storage uses its own assigned cost percentages under Notice 2025-08, with separate tables for grid-scale and distributed battery storage. The notice assigns percentages to components including battery cells, pack or module packaging, inverter or converter parts, battery management systems, thermal management, and the container or housing.

Domestic content compliance goes smoother when it’s built into procurement instead of checked after the fact. Here’s a workflow that keeps sourcing decisions aligned with the tax position before equipment gets locked in.

1. Confirm whether the project owner intends to claim the domestic content bonus at all

2. Identify the exact beginning of construction date and the applicable threshold

3. Determine the project type and pull the matching Notice 2025-08 table

4. Request exact model and SKU information from suppliers, along with sourcing documentation

5. Build the domestic content calculation before procurement gets finalized, not after

6. Set up an approval step for any equipment substitution during the project

7. Reconcile the final installed equipment list against the original calculation before certification

That last step matters more than it looks. A calculation built on paper equipment doesn’t help anyone if the equipment that actually gets installed is different.

Yes. Domestic content eligibility is tied to the equipment actually incorporated into the project upon completion of construction, not the equipment originally specified on the bid. A module, inverter, racking, or storage substitution can change the calculation even when the replacement part performs identically to the original.

Picture a project designed around a domestically qualifying module, but a distributor swaps in a different SKU because of availability. The electrical specs match perfectly. The domestic content percentage might not, especially if the replacement module sources its cells or wafers differently.

Flag every substitution for review before installing replacement equipment whenever the project owner intends to claim the domestic content bonus. A quick check before the swap goes in is far easier than reworking the calculation after the system is energized.

The taxpayer claiming the 48E credit is responsible for satisfying and certifying the domestic content requirement, not the installer. Per the current Form 3468 instructions, the taxpayer must attach a domestic content certification statement declaring that the qualifying steel, iron, and manufactured products were produced in the United States, and that statement gets signed under penalty of perjury.

Solar contractors, EPCs, and distributors don’t sign that certification. What they do control is the equipment records and sourcing documentation the taxpayer needs to make that certification accurately. That distinction matters for how you position your role on a project, and it keeps you out of tax-advice territory while still being genuinely useful.

Good documentation is where installers actually add value on domestic content, even though they’re not the ones filing the certification. Splitting the records into what the taxpayer needs and what installers should keep on hand makes the handoff cleaner for everyone.

• Domestic content certification statement, signed and attached to the applicable tax form

• Final domestic content percentage calculation and the safe harbor table used

• Confirmation of which notice (2023-38, 2024-41, or 2025-08) the calculation relies on

• Manufacturer, supplier, and exact model or SKU numbers

• Module, inverter, racking, and battery documentation showing country of manufacture

• Final bill of materials and equipment schedule

• Purchase orders and invoices tied to the installed equipment

• Distributor substitution notices and approved change orders

• Dated supplier representations regarding domestic content status

• Documentation showing whether domestic crystalline silicon cells and domestic wafers are being claimed for module percentages

• Records supporting any mixed-source calculation, where the same component type comes from both domestic and foreign suppliers

• As-built equipment list reconciled against the original calculation

• Version of the domestic content calculation used before final certification

The IRS’s domestic content bonus credit overview lays out the certification and elective-payment phaseout rules in more detail. The exact records a taxpayer needs can vary by calculation method, project structure, and tax position. Project owners should confirm their specific recordkeeping requirements with their tax advisor rather than treating this list as an exhaustive legal requirement.

A single piece of equipment can affect both calculations at once, but clearing one test never establishes the other. A domestically manufactured inverter might satisfy the manufactured products requirement while still failing the FEOC material assistance test if its subcomponents trace back to a prohibited foreign entity. Treat the two as parallel checks on the same equipment list, not one combined sourcing decision.

If you haven’t run the FEOC side of the analysis yet, the FEOC supplier checklist walks through the material assistance cost ratio and the current thresholds by project type.

Planning a 48E-eligible solar or storage project? GreenLancer can support the commercial permit design and engineering documentation that keeps your equipment selections, project drawings, and approved substitutions aligned from start to finish.

Complete the form below to get started.

For a solar project beginning construction during 2026, at least 50% of the manufactured product cost must qualify as domestic content, and all applicable steel or iron products must be 100% U.S.-made. The manufactured products threshold rises to 55% for projects beginning construction after 2026.

No. Domestic content is optional and only affects whether a project earns the bonus. A project can qualify for the base 48E credit without meeting domestic content at all, provided it satisfies the credit’s other requirements, including any applicable FEOC restrictions.

No. Domestic content is an optional test that increases the credit amount. FEOC is a mandatory restriction that can eliminate the credit entirely. They’re governed by different IRS notices and calculated using different formulas.

No. The 100% domestic requirement applies only to steel or iron products classified under that specific test. Module-level components like cells, glass, and encapsulant each carry their own assigned percentage under the manufactured products test, and a module can contribute significantly to the total even without every component sourced domestically.

Yes. Domestic content is evaluated based on the equipment actually incorporated into the project upon completion of construction. A late substitution, even one with identical electrical specs, can lower the domestic content percentage below the required threshold.

Installers should retain the final bill of materials, model and SKU numbers, country-of-manufacture documentation, purchase orders, substitution notices, and the version of the domestic content calculation used before certification. The taxpayer uses these records to support the certification they file with the IRS.

Yes. The manufactured products threshold is tied to the beginning of construction date, not the year the project is placed in service. Under the current §48E schedule, the threshold is 50% for projects beginning construction during 2026 and 55% for projects beginning construction after December 31, 2026.

The taxpayer claiming the 48E credit certifies domestic content compliance by attaching a signed certification statement to their tax filing. Installers and EPCs are not the certifying party, though their procurement and sourcing records are what make an accurate certification possible.