If you have an Ammeter in the External Circuit, then you should be able to find the quantity in the Transient result plots under the "BranchCurrent" category. If this is placed right after the battery, then the total electrical power would just be BatteryVoltage*Ammeter, and you can calculate the average power directly. This will account for all losses included in the electric/magnetic conversion process defined in the simulation. If there are additional losses outside the scope of the model, then you would either add these at the input, or subtract from the output (often frictional losses and corelosses are considered as post-processing, but could be defined so that they affect the power conversion process).
You are navigating away from the AIS Discovery experience