If I were to rent a place out, this is what I would do:
I would include utilities in the rent for about double what the average utility bill is, AND I would have written into the lease that anything over 15% more than the normal utilities for that month will be charged to the tennant (security deposit). You'd have to get the average useage (not cost) for everything for the past 12 months. Add it all together and put that in the lease that anything over XX in useage will fall to the tentant to pay the difference.
So lets say that from January to June, you use 100 gallons of water a month. July to September, you only use 50 a month. And October to December you use 200 gallons a month. I'd then put it in the lease that either they're allowed 1,350 gallons a year, and anything over that they have to pay. Or do it month to month, and give them a limit of 112.5 gallons.
We had this happen at a place in college (the annual limits). We knew we were paying a lot more than we were using, but it was just easier than to split 4 bills among 4, and then 3, people (Apartment was still best deal we could find at the time). We would have come in WAY underneath their limits if it weren't for a subleasor we had over the summer that would do a load of laundry consisting of 2-4 articles of clothing probably 4 times a week. But we were also watching our utilities, since we knew we could indeed go over.