Define your purchasing strategy with a photovoltaic wholesaler (pallet, loose, lead times)
Pallet purchase vs loose purchase: thresholds, delivery constraints and impact on your margin
| Mode | Typical quantity | Delivery constraints | Impact on margin |
|---|---|---|---|
| Pallet | 25 to 36 modules | Appointment, unloading equipment, storage space | Better €/Wp, lower unit costs |
| Loose | 1 to 10 modules | More flexible, but higher fixed costs | Extra cost to pass on, otherwise gross margin falls |
At a photovoltaic wholesaler, pallet buying suits repeat jobs. Loose buying suits top-ups. Break out transport and re-delivery contingencies on the quote.
Price in euros per peak watt: compare like for like in power and technology
| Technology | Relevant comparison | Purchase range (€/Wp) |
|---|---|---|
| Mono PERC | Same unit power, same range | 0.10 to 0.16 |
| TOPCon | Same, pay attention to efficiency | 0.12 to 0.18 |
| HJT | Same, often premium | 0.14 to 0.22 |
Compare equivalent power, format and warranty. A larger 450 Wp module reduces the number of modules, but can increase installation time and handling constraints.
Stock that moves fast: secure your jobs without carrying risky inventory
Lock the reference with a reservation confirmation and an availability date. Prepare an approved substitute solution (certifications, declared module-inverter compatibility). Avoid long-held stock. References change over quickly, and an extension or replacement soon becomes unmanageable.
Compare modules to optimise installation and profitability (format, power, layout)
Unit power and format: fewer modules, fewer fixings, shorter installation time
At equal installed power, a higher-power module reduces the number of panels, clamps and handling operations. When buying, think first in €/Wp delivered to site, then convert that into installation minutes per module. Example for 6 kWp.
| Module power (Wp) | Modules for 6 kWp (u) |
|---|---|
| 400 | 15 |
| 450 | 14 |
| 500 | 12 |
The right format is the one that fits the roof without multiplying rail cuts and remains manageable according to your methods.
Roof layout: anticipate module count, offcuts and safety constraints
The layout is decided before ordering. You lock the grid, fixing centres and no-go zones. The goal is to limit offcuts and avoid an area that cannot be completed.
- Measure the usable dimensions, not the gross dimensions.
- Include eaves, ridge, valleys and penetrations.
- Reserve access paths and lifeline routes.
Managing references: avoid one-shot ranges that cannot be completed or replaced
Avoid one-shot modules that disappear with the next container. Secure a stable reference and a substitution option. With your photovoltaic wholesaler, require range continuity, connector compatibility (MC4 or equivalent) and consistent electrical characteristics for strings (Impp, Voc), otherwise you end up carrying the after-sales burden and extensions. For more on sizing and trade-offs, see sizing your self-consumption system.
Buy compliant: documents and certifications to require from the photovoltaic wholesaler
Module and inverter certifications: what to check before ordering
Before you confirm a basket with your photovoltaic wholesaler, require a test report and compliance evidence identifiable by reference and serial number.
| Equipment | References and documents to obtain |
|---|---|
| Modules | IEC 61215, IEC 61730, datasheet, flash list, warranty terms |
| Inverters | EN 50549 (grid certificate), IEC 62109, EU declaration of conformity (CE), French manual |
Declared module-inverter compatibility: reduce disputes and secure commissioning
Ask for declared compatibility and archive the string sizing. Check Voc at Tmin, Isc, the MPPT range, number of MPPTs and admissible current per input. On the quote and delivery note, freeze the exact references (and firmware if required).
Documents for grid connection and insurance: build a solid file from the purchase stage
From the purchase stage, put a file together. Invoice and delivery note (references, quantities, batches), datasheets, inverter grid certificate, manuals, and the mounting system documents (fire classification, DTA or ATec if integrated mounting). File everything by serial number for traceability and for the insurer, and on the cover side, also remember to check your contract.
Warranties and reliability: secure your liability over 10 to 25 years
Product warranty vs performance warranty: read the terms and exclusions carefully
| Warranty | Duration (years) | Key point to watch |
|---|---|---|
| Product | 10 to 25 | Material, manufacturing, frame, junction box, connections defect |
| Performance | 25 | Measured power according to protocol, often via laboratory |
The product warranty covers defects. The performance warranty covers output over time. Your risks lie in the written terms and exclusions. Transport, storage, clamp tightening, electrical incompatibilities, aggressive cleaning — all of these can fall outside the scope. Ask for installation requirements and the evidence procedure before locking the quote.
Manufacturer strength: range continuity, presence in Europe and after-sales handling
Over 10 years, a manufacturer changes faster than a module. Secure your liability by checking for a European entity, a clear RMA process, and continuity of references (format, connectors, frame colour) for replacement. Your photovoltaic wholesaler should be able to state after-sales lead times and who bears logistics costs.
Traceability and serial numbers: useful proof in case of failure or claim
Keep a traceable file. Record serial numbers and map them by array and by string. Archive the delivery note, serialised list, datasheets, IEC certificates, pre-commissioning photos, and handover report. In the event of failure or claim, this is your chain of evidence with the manufacturer and insurer. Before starting, also check the photovoltaic panel regulations before installation to avoid non-compliances that weaken your files.
Turn your purchase into a selling price: margin, discount and clean costing
Supplier discount and company margin: do not confuse them and protect your profitability
The discount negotiated with a photovoltaic wholesaler lowers your purchase cost. It does not replace your gross margin, which covers fixed costs, cash flow, after-sales and reference-change risk. Keep the discount in the purchase. Do not automatically "give it back" to the customer unless that is a deliberate, costed strategy.
Cost items to include: transport, handling, waste, small materials and installation time
- Transport and handling, with a surcharge if delivery is split.
- Waste. Breakage, scrap, reserve modules for replacement.
- Small materials. Fixings, rails, clamps, marking, consumables.
- Installation time. Format and unit power affect the number of modules and hours.
Adjust your prices without guesswork: a simple method for clear, defensible quotes
Work in €/Wp. Calculate a unit cost. Apply a target mark-up rate, then break it down into quote lines. You justify each item, without mixing discount and margin. For more on margin tracking and slippage (hours, unforeseen work), see calculating your margin and tracking site-hour slippage.
| Item | Base (€/Wp) | Rule |
|---|---|---|
| Net module purchase | A | List price minus discount |
| Ancillary costs | B | Transport, waste, small materials, handling |
| Cost price | A+B | Unit cost, traceable |
| Sale price excl. VAT | (A+B)/(1-t) | t = mark-up rate |
