Splitting utilities on the same meter

[Miranda Warner]

We are renovating a true duplex, and we are converting the garage into another unit. The place is currently submetered for the two duplexes, and the garage utilities are tied to one of the units. Do you have any advice on how to split the utilities between the garage unit and the other unit it is metered with? We will be living in the garage unit for a couple years, but eventually we will have it managed by someone else and will not be able to be as hands on with billing utilities.

Are there any other options than to just charge a flat rate for utilities? Thanks!