Same Device Three Bluettis show different useage?

Total newbie but - have AC200P, EB3A and EB55 and when I pug in Only my monitor AC200 says its pulling 45W the 55 says its pulling 30W and the EB3a says its pulling 18W ?

Any ideas?

I promise all other conditions equal

Welcome @VKStephenson that will be caused by the different size of inverters in each unit. You will get the same results whatever you plug into it.