Charging for Utilities in California

[Marshall Rousseau]

I have a property where the adu and main house share utilities. adding separate meters isn't an option at this point in time.  In the past, I have rented them out with utilities included.  When rented out next, is there any advantage to lower the rent, and instead, charge a flat utility fee? Is there any legal way to guard against a disgruntled tenant doing something like running the water 24/7? Located in the peoples republic of California. Thank you!