A thermostat with a fixed temperature will help but even then, expect the utilities to be higher than when you occupied the apartment...a lot higher. Set the rent in expectation of a higher utility bill and they place a dollar cap on both the water and the electricity or a dollar cap for both combined. Put this cap in your lease with wording that the overage will be added rent. State the week it will be due. Never let the tenant tell you that they have the rent but not the utility surcharge. If they do not have both, they do not have the rent. Tell your tenant what week to expect the bump and require it to all be paid at one time. Not spread out over the remainder of the month. Do not try to manage their behavior toward lowering the bill. If the bill is high enough, they will either pay or manage their own behavior. Also, put it in the lease that they can not "take in wash."