Separating water/radiator heating back to tenants - ROI check

[Abby S.]

My 4 unit is at $4800 in gas for the year with budget billing, which is on me to pay. This is one large water heater tank (75gal)  in the basement, alongside a boiler that feeds the radiators throughout.

In planning for some work in the building, I have the opportunity to install separate water heaters in each unit. A few questions:

- If I can offload that cost amongst the tenants assuming a 6% cap rate, $4800/.06 = $80k in added equity?

- The work would be part of a larger project, but let's say that with running gas, electric & installing separate tanks, as well as furnaces - I'm at $18k (total swag) for the parts/labor on all four units. Then the ROI on that is $18000/4800 = 45 months?

- Is the simple CoC return math here 4800/1800 = 27%?