I think the answer is “it depends”.

The calculated peak load is the peak requirement on the module. So it is calculated before any plants are actually dispatched and before any gap filling imports occur (i.e. you may not have sufficient capacity in your plants to meet the peak and so have to resort to imports). However, if you specify an import target, those imports are deemed to occur before the module is dispatched, so they are deducted from the overall module requirements before the peak load is calculated.

The basic order of calculations for a module is as follows:

• Calculate Total Energy Requirements on Module (based on domestic demands, earlier export demands, and losses and transformation in any modules above the current module, and deducting any import target for the output fuels of that module).
• Prepare Load Curve
• Calculate Required Reserve Margin
• Calculate Planned and Unplanned Capacity Additions
• Dispatch Processes
• Calculate Outputs from Module and deal with any shortfalls (which may cause additional imports) and surpluses (which may cause exports)
• Calculate Inputs to Module