SAM nameplate power different from manufacturer

Can you explain why the module nameplate power displayed in SAM is different than the manufacturer's rating? For example Canadian Solar rates the CS6P-255P at 255W but SAM shows nameplate capacity = 8118Wdc for a 32 module array, or 253.7Wdc per module. This difference causes a little bit of extra work when entering system costs in terms of $/nameplate watt.

Dear Tom,

When you use the "CEC Performance Model with Module Database" option in SAM, it calculates the module's maximum rated power (Pmp) at STC from the rated maximum voltage (Vmp) and current (Imp) provided in the CEC database for that module. In the case of the CS6P-255P module, the database values are Imp = 8.4 A and Vmp = 30.2 V, so SAM calculates Pmp = 8.4 * 30.2 = 253.68 W.

On the manufacturer's data sheet for that module, they show Vmp=30.2 and Imp=8.43 and a "nominal" maximum power of 255 W. The nominal power is different from the rated power.

That means that any $/W costs that you specify on SAM's System Costs page will be calculated based on the rated Pmp reported by the manufacturer instead of the nominal value they use in the module's name.

Best regards,
Paul.