Estimating utilities for multi-families in STL

[Shelley W.]

I'm analyzing multi-family properties in STL south city, and I'm having trouble figuring out how to estimate utilities. I know landlords often pay water/sewer/garbage in STL. And I know I can call the utility company about a specific property, but I'm wondering if people have numbers based on experience, or numbers they use as ballpark figures when they're analyzing properties. Right now I'm using $115/month water/sewer/garbage for 1br / 1ba, so I'd allow $230 for a 1+1 duplex, but I don't know how that translates 2+1 and 2+2 and 3+2 properties. If I use my 1br / 1ba numbers and just multiply that times the number of bedrooms a unit has, that adds up to a lot of $ fast and I'm worried that I'm overestimating utilities using that method. Does anyone have a better method for ballparking these numbers for initial analysis of properties?