This has been tested and, no, the location doesn’t make a difference to the necessary power output on a bike. Weight is weight as far as the system is concerned

This has been tested and, no, the location doesn’t make a difference to the necessary power output on a bike. Weight is weight as far as the system is concerned. Another thing that might come into play is simply holding the backpack on your back. If you put that same weight on a saddle bag or frame bag, your power output won’t need to change but you’re not constantly carrying it physically on your back.