currently it is impossible to distinguish between whether a hole is an "input" or "output". i spent a while trying to figure out what i was doing wrong with the MV->LV transformer (as i assumed it worked like the storage unit, takes power from all sides except the hole, outputs power to the hole) but its the opposite to that. the same goes for input-output hatches, but those at least you can right click on to see whats what.

rough concept

I agree that the sides of hatches can be very confusing to look at. There needs to be some change made there.

To clear up your confusion with the transformers, the hole always represents the higher voltage. This is so that there are more faces for the lower voltage to input/output to/from. That way you can actually transform one 1024 EU/t (MV) to four 256 EU/t (LV) cables. So, if you were to use an LV -> MV transformer, the hole would be the output that MV power comes from.