Utilities In a Multi-Family

[Alex Del]

Hi all, 

I have a 2-family home where I am currently trying to come up with a plan for how to have the tenants cover the utility costs.  Unit 1 has oil heat through forced air, it only serves that unit and has its own oil tank, so that one is easy; the tenant of Unit 1 pays for their oil.  

However, the second furnace heats the hot water for both Unit 1 and 2, as well as serves to heat the baseboard heat in Unit 2; this is served by its own oil tank.  What's the best way to chop that up as far as that oil bill goes?

Lastly, the electric has 1 meter going into the home, which goes to the main panel which serves Unit 1, and off the main panel there is a subpanel for the electric in Unit 2, however no 2nd meter.  As far as electric bill goes, what's the best way to divide that up, if any?  I'd like to avoid including the electric in the rent so as to deter the tenants from "running the A/C with the windows open because they like the breeze", and if they do it's on them.

Thanks for any insight you can offer!

Alex