By Alex Zhu, CEO
Not all wafers entering U.S. solar cell factories are the same, which is drawing scrutiny from federal lawmakers, regulators and the solar industry. What kind of wafer comes into the factory can determine whether a product is truly a U.S.-manufactured solar cell — or a substantially completed foreign cell receiving only limited finishing in the United States instead.
For developers, module manufacturers, insurers and tax-credit investors, this can affect domestic content calculations, eligibility for federal incentives, and exposure to tariffs or penalties.
What Is the Difference?
A gray wafer is an unprocessed silicon wafer that cannot yet convert sunlight into electricity. It becomes a functioning solar cell only after it moves through several critical manufacturing steps, including surface treatment, diffusion, coating, metallization and testing.
A blue wafer has already undergone some of the most important steps in that process. Most significantly, its P/N junction — the semiconductor structure that enables the conversion of sunlight into electricity — has already been formed. An anti-reflective coating typically gives the product its blue appearance.
In simple terms:
- A gray wafer is the raw material used to manufacture a solar cell.
- A blue wafer needs only a few final process steps to become a completed solar cell.
The location of where the core cell-making processes, specifically P/N Junction, occur can influence the product’s country of origin designation and its treatment under U.S. tax and trade rules.
Why the Issue Is Receiving Attention Now
Some manufacturers are reportedly importing blue wafers into the United States, completing a limited number of remaining steps domestically, and marketing the finished product as a U.S.-made solar cell.
In July 2026, a bipartisan group of federal lawmakers asked U.S. Customs and Border Protection and the Internal Revenue Service (IRS) to investigate whether imported blue wafers are being used to avoid trade duties and improperly claim federal manufacturing tax credits. The lawmakers argued that these products have already undergone the essential processing that enables them to generate electricity before arriving in the United States. Reuters reported on the lawmakers’ request.
The concern is straightforward: Applying finishing steps to a nearly completed foreign cell is not the same as manufacturing a cell in the United States.
Why Solar Buyers Should Care
For project developers and module manufacturers, relying on unclear or unsupported country-of-origin claims can create risks in several areas.
1. Domestic content qualification
The IRS domestic content framework recognizes a difference between U.S.-manufactured solar cells made with foreign wafers and those made with U.S.-manufactured wafers. Under its elective safe harbor, each sourcing configuration receives a different assigned cost percentage when determining whether a project meets the domestic content threshold.
A cell made in the United States from a foreign gray wafer may contribute domestic value as a U.S.-manufactured cell, even though the wafer itself remains foreign. A product imported after the P/N junction has already been transformed via the diffusion process may already meet the definition of a functional solar cell.
If a blue wafer is incorrectly represented as a wafer rather than a partially completed foreign cell, the project’s domestic content calculation could be overstated.
2. AD/CVD and tariff exposure
Country-of-origin rules for antidumping and countervailing duties do not necessarily follow the same standards used for tax credits or general customs classifications.
For solar cells, the formation of the P/N junction has historically been a critical factor in determining origin under AD/CVD rules. Completing metallization or other downstream steps in the United States may not change the foreign-origin designation established when that junction was formed. A product presented commercially as U.S.-made could therefore still carry foreign-origin duty exposure.
3. Documentation and audit risks
The entity claiming a domestic content bonus must maintain records that substantiate the claim. IRS Notice 2025-08 specifically reinforces the entity’s responsibility to retain documentation supporting domestic content eligibility.
A general “Made in America” statement may not be enough. Customers need documentation showing what material entered the factory, where the P/N junction was formed and which manufacturing processes occurred in the United States.
Questions Buyers Should Ask
Buyers should ask suppliers:
- Does your U.S. cell manufacturing process begin with an undiffused gray wafer?
- Where specifically is the P/N junction formed?
- Which cell-processing steps occur in the United States?
- How is the imported material classified when it enters the country?
- Can you provide auditable documentation supporting the cell’s origin?
- Who assumes responsibility if those representations are challenged?
- When could we set up a visit to your factory to walk me through each processing step?
If a supplier cannot answer those questions clearly, the customer may be assuming more risks than the purchase agreement suggests.
Only Buy Cells Made from Gray Wafers
The blue wafer debate points to a larger issue facing the U.S. solar market: the difference between locating a few production steps in America and building meaningful domestic manufacturing capability.
At ES Foundry, solar cell manufacturing begins with gray wafers. The critical processes that transform those wafers into functioning solar cells take place at our Greenwood, South Carolina facility. That distinction provides customers with greater transparency into how and where their cells are manufactured.
As tax and trade enforcement become more rigorous, buyers need a traceable manufacturing process, defensible documentation and a supplier prepared to stand behind its claims.
Before counting a solar cell toward a tax credit or domestic sourcing commitment, look beyond where the final steps occurred. Ask where the cell truly became a cell.
This article is intended for general informational purposes and does not constitute tax or legal advice. Project owners and manufacturers should consult qualified advisers regarding their specific circumstances.