Most of the world's solar panels, cells and wafers are made in China, and most panel factories are in Jiangsu, Zhejiang and Anhui, with large plants also in other provinces. Next to the big manufacturers there are many smaller module assemblers and a large number of trading companies that sell panels, inverters and batteries under their own names.
Solar buyers rarely receive empty boxes. The usual problems are lower power than the label, lower-grade cells, panels that are not covered by the certificates shown, "Tier 1" claims that mean nothing, and warranties that no one will honour. This guide explains what to check.
Manufacturer, assembler or trader
Integrated manufacturers make wafers, cells and modules, or at least cells and modules.
Module assemblers buy cells and assemble them into panels. Quality depends on which cells they buy and how well they laminate.
Traders buy panels from either and sell them, sometimes under their own brand. A 25-year warranty from a trader is only as good as the trader's future.
"Tier 1" is not a quality grade
The well-known Tier 1 list is a ranking by a research firm based on how many large bank-financed projects have used a manufacturer's own-brand modules. It is about bankability, not about the quality of a particular panel, and it covers the manufacturer, not traders reselling its panels or factories making them for other brands. If a supplier claims to be Tier 1, ask which list and which edition, and check the company name.
Certificates
Panels sold in most markets need certification to IEC 61215 (design and performance) and IEC 61730 (safety), issued by a recognised body such as TÜV, Intertek, UL, CSA, CQC or Bureau Veritas.
The certificate lists the manufacturer, the factory address and the exact model series and power range. Check that your model and power are on it, and that the factory on it is the one that will make your panels.
Verify the certificate number with the issuing body. Most offer an online certificate database.
Some markets need more, for example local approvals or specific listings for grid connection. Ask your installer or distributor what applies.
What to put in the specification
Cell technology and maker, and cell grade (A grade only).
Power, positive power tolerance (for example 0 to +5 W), efficiency and dimensions.
Glass thickness, frame material and thickness, junction box and connector maker and type.
Flash test data for every panel, by serial number, and EL (electroluminescence) images showing no cracked cells.
Product and power warranty terms, and which company gives them.
Inverters and batteries
For inverters, check the grid code and safety certificates for your country and that the model you buy is the one listed. For lithium batteries, ask for the cell maker and type, the UN 38.3 transport test report and the safety data sheet, which you need to ship them, plus any safety certificates your market requires.
Before shipment
Compare labels with the order: model, power, serial numbers.
Check flash test data and EL images for sampled panels against their serial numbers.
Look for visual defects: broken or chipped cells, bubbles, scratches on glass, frame damage, bad sealing of the junction box.
Check packing and loading: corner protection, pallets, and how the pallets are secured in the container.
Questions to send the supplier first
Which factory makes these panels? Please give its full Chinese name, unified social credit code and address.
Whose cells are used, and which grade?
What are the IEC 61215 and IEC 61730 certificate numbers, and do they list this model, this power and this factory?
Will you provide flash test data and EL images for every panel?
Which company gives the product and power warranty, and what happens if that company stops trading?
See also how to check certificates from China and Suzhou and Wuxi suppliers.
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LocalAuditChina is an independent verification service, not a certification body or a solar test laboratory.
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