There are a couple of issues here.
It is not idiomatic to say "the water usage of me" or "the water usage of him". We say "my|your|his|her|our|their water usage".
The hat of me (no)
My hat (yes)
For that reason, native speakers naturally tend to avoid phrases like "the water usage of him and me" or "the water usage of Bob and me". Does that mean no native speaker would ever say "The water usage of Bob and me is different"? No, it does not; but such usage is an outlier statistically.
A native speaker with a developed sense of grammatical foresight would not make "water usage" the subject of the sentence, because if they do, they get into hot water when trying to express the idea that the thing is not something shared but two things which are distinct and being compared; and that problem persists even if the noun is countable:
The friends of Bob and me...
Are we talking about Bob's friends as distinct from my friends, or about our mutual friends?
The water usage(s) of Bob and me...
Are you and Bob roommates or housemates? Neighbors? Making a usually non-count noun countable helps to clarify, but there is still some dissonance: "the hat of me".
To express the idea of distinct comparands clearly, we state each comparand separately:
Bob's water usage and mine vary considerably.
Bob's water usage and my own vary considerably.
My water usage and Bob's vary considerably.
My own water usage and Bob's vary considerably.
Bob's water usage and my water usage are not all that different.