How to calculate utilities for your tenant with one meter?

[Vera Todoriko]

I am newby. We just purchased a two family house in a prominent area of RI, Barrington. We did some renovation in the kitchen, paint the walls and kitchen cabinets.  All 4 appliances are high end and brand new.  The family of four is applying now for our 3 bedroom appartment. We only live here for 1.5 month and its hard for me to figure out how much heat and electricity expenses I should include in the rent, because we only have one meter for electricity and one oil tank. We also have 6 mini splits for heating/airconditioning, 3 on our first floor ( for landlord) and 3 on a second and third floor for rentals. Also, should I include water expenses too?  I appreciate all your input.