See, that sounds like a part time job waiting to happen. Are we gonna get a spreadsheet for how many minutes everyone showers or count squares of toilet paper? My old roommate tried that and we spent more time arguing over the electric bill math than we did using the electricity. Sometimes simple is just better, even if it's not perfectly fair.
Ugh that reminds me of when my friend tried to split the cost of a pizza based on who ate what toppings. Total mess. Charlieo29 is right, it just causes stress over nothing.