Six workshops can contribute to one rooftop bill of materials. A module line makes the glass, another plant extrudes the racking, a cable mill supplies the DC runs, a connector maker supplies the mating pairs, a sheet-metal shop builds the combiner boxes, and a printer produces the labels. Each will quote happily. Nobody in that chain is responsible for whether the six lots arrive together with documents describing the same system.
That coordination is the work behind project-scale solar sourcing. This guide breaks the bill of materials into evidence-sized pieces and is a downstream chapter of our solar, storage and power equipment sourcing guide, which covers inverters, stationary storage and grid-side hardware in the same shipment.
1. What is deliberately outside this guide
Folding panels, solar street lights and small solar lamps are finished consumer goods with different standards, packaging and buyers. They are covered by our backup power and solar equipment hub, with dedicated guides to foldable panels and street lights. Here the assumption is a project BOM that a consultant will review before installation.
We are a China sourcing agent and freight forwarder, not a module maker, a test laboratory or a certification body. The standard names below are references used in procurement documents. No brand, price, wattage, minimum order or delivery promise appears on this page.
2. Start with the BOM, line by line
Write the system as a list of line items, each with a model identifier, a quantity, a workshop and the evidence that must travel with it. Then ask every supplier to quote against that exact list. A bundled quotation that hides the BOS lines behind one figure makes substitution invisible and comparison impossible.
| BOM group | Typical supplier | Evidence that belongs in the file |
|---|---|---|
| Modules | Module assembly line | Design qualification report, flash test data and electroluminescence images |
| Racking and fasteners | Extrusion and metal fabrication plant | Material and coating specification, structural calculation for the stated wind and snow zone |
| DC cable and connectors | Cable mill and connector maker | Cable designation and cross-section, connector standard and mating compatibility statement |
| Combiner and protection | Sheet-metal and assembly workshop | Enclosure rating, fuse and surge device list, wiring diagram and terminal plan |
| Labels and manuals | Print and packaging supplier | Approved artwork, language set and the label content required at destination |
3. Module evidence is more than a datasheet
Design qualification and safety standards commonly referenced for modules include IEC 61215 and IEC 61730. Ask for the report, the laboratory, the model on its cover and its date; then check that the bill of materials behind the report matches the glass, cells, encapsulant, backsheet, junction box and cable actually ordered. A substitution in any of those can change the validity of the file.
Production evidence is separate. A flash test records electrical performance for each module, and electroluminescence imaging reveals microcracks and cell defects that a visual inspection misses. Agree the sampling basis, the acceptance rule and the retention of images before the deposit. Ask also how modules are packed, stacked and protected against moisture, because a good test result does not survive a badly loaded container.
4. The DC side is where small parts cause large failures
Cable and connector line items look trivial on a quotation and are disproportionately represented in field faults. DC cable designations such as H1Z2Z2-K or PV1-F describe construction and temperature and UV behaviour, not just a cross-section. Connectors and junction boxes have their own standards: IEC 62852 for connectors and IEC 62790 for junction boxes are the references a project file commonly cites. The point that matters commercially is mating compatibility.
Mixing connector families from two workshops is a classic failure: the parts look interchangeable, seat with a click, and then overheat under load. Require a written statement that the connector, the junction box lead and the extension cable form one approved mating set, and freeze that set in the BOM. For coastal sites, add salt-spray and UV exposure to the specification rather than assuming an indoor rating transfers outdoors.
5. Racking is a structural product
Mounting structure is specified against a site, not a roof type. Wind zone, snow load, roof covering, tilt, corrosion class and fastener material all move the design and the coating. Ask for the structural calculation for your stated conditions, the alloy and coating specification, and the compatibility of fasteners with the roof material. A racking quote that omits clamps, rails, earth bonding or the fixing kit is not a complete quote.
Then check how the long items are packed. Racking is bulky but robust and should travel separately from glass; optimising the container mix is a planning job, not an afterthought at the warehouse. Our pre-shipment inspection service covers dimensional and packing checks on a running batch, and our factory verification process covers the supplier side before a deposit moves.
6. One evidence set per line, one revision for the whole BOM
Keep a folder for each workshop and a master index that names the approved revision of the entire BOM. When a supplier changes a cell, a coating, a connector or a label, ask in writing which reports are affected. This is the same discipline an EPC consultant applies, and it is much cheaper to apply before shipment.
| Control point | What is frozen | Who signs |
|---|---|---|
| Golden sample | One physical reference per line item, with dated photographs | Buyer and supplier |
| BOM revision | Model identifiers, quantities, mating sets and document references | Buyer’s project engineer |
| Artwork and labels | Logo files, language set, rating plate content and carton marks | Buyer’s brand owner |
| Release | Inspection protocol result and the packing list for each lot | Agreed inspection authority |
Approved artwork is a documentation change as well as a design one. A printed carton, a translated manual and a rating plate each need a formal approval round; our packaging guide and private label guide mark that boundary. We gather and sort the evidence, flag any page naming a different model and issue nothing ourselves.
7. Mixed cartons and the consolidation plan
A project container mixes fragile glass, long racking, cable drums, small boxes of connectors and printed cartons, usually from workshops with different schedules. Decide the packing hierarchy at order stage: what is palletised, what is boxed, what is bagged inside another carton, and how every loose item appears on the packing list. Otherwise the consignment arrives with parts that nobody can account for.
Consolidation is where a sourcing and freight partner earns its keep: the lots can be received, checked, photographed and loaded as one shipment with one document set instead of several consignments each carrying fixed charges. Our services overview explains that coordination, and the DDP service page covers where the delivery term meets importer-of-record responsibility. Classification of the individual line items belongs with a licensed broker; we publish no rate or duty amount.
8. A first enquiry that gets a usable answer
Send the system size and site conditions, the module type you are considering, the racking and roof description, the DC voltage class, the cable and connector families, the destination and the standards your consultant has named, your quantity breaks, artwork needs and whether samples come first. A BOM spreadsheet or a photograph of the existing array is enough to begin. Send an enquiry or use either WhatsApp button on this page.
9. Frequently asked questions
Can one supplier provide the whole project BOM?
Some will offer to, often by reselling other workshops’ parts. That is workable if every line item still has its own model identifier, report and inspection record. A single bundled figure that hides the parts list is not comparable.
Why does connector compatibility need a written statement?
Because parts from different families can appear to mate while failing under load. Freeze one approved mating set covering the junction box lead, the connector and the extension cable, and keep it in the BOM revision.
Is a module design qualification report enough?
No. It covers a design. Production evidence such as flash test data and electroluminescence images, plus a check that the materials match the tested configuration, is a separate part of the release.
Who decides the duty treatment for a mixed container?
A licensed broker, line by line, because the components are classified separately. We coordinate the packing list and documents at origin and state the importer-of-record split in writing; we do not publish rates or classification codes.
Do you quote a price per watt or a minimum order?
No. Both depend on the approved BOM, the destination, the specification and volume. We quote against your written list after sample approval, with the freight plan included in the comparison.
Need a Quote? Message Us on WhatsApp
You have read through the bill of materials and the evidence behind each line, so here is the direct line. Send your project BOM, the site conditions, the destination standards and your quantity breaks; our sourcing team will return comparable quotations and a consolidation plan.
Chat on WhatsApp → Use the Quote Form
WhatsApp and phone: +86 186 7676 3055 | Email: info@cinosourcing.com
It helps to name the roof or ground conditions, the DC voltage class, the connector family already in use, the artwork and manual languages, and whether samples come before a batch. A spreadsheet or a photograph of the existing array is plenty to start. No obligation and no long form.