I'm expecting this is just the bus power to the "modules", the different sections of the ISS. I rather expect most modules probably have a down-converter & run

I'm expecting this is just the bus power to the "modules", the different sections of the ISS. I rather expect most modules probably have a down-converter & run off something like 12, 24, or perhaps the shuttle's 28Vdc. ISS isn't afraid to waste some power. The photovoltaic arrays send power to a "sequential shunt unit", which adds resistive load to maintain a constant voltage/current from the array. Admittedly, not applicable when running off battery, but it shows that power efficiency is not really the priority.