boiler replace - yay or nay

[Alissa Hyder]

Hi There, I'm a newby investor that ventured into my first multifamily that I am working to stabilize. 

The property is out of state for me (also a first!) located in Cincinnati. The property is a 4 units - 2/bed, 1/bath each. I pay the gas, sew and trash. 

It is heated with a gas boiler system that is about 15 years old but still in good condition. It does not have a thermostat that can be adjusted regularly like modern day tech. It is either on or it is off and I'm told it is about 60% efficient. The gas bill was $500-800 p/mo over the winter. Average p/mo for the year is around $400. I talked to 3 different HVAC companies - one of which did substantial work and research to figure out best option to cut cost. Sounds like most cost effective approach would be to replace the unit with a new system that is 96% efficient. Quotes from 2 companies was $14k-16k (based on photos). The 3rd company (did the research and toured the property) was $19k - This is actually negotiated down from their initial quote of $23k.

I am trying to decide if this is a good idea or not. It is hard to know how much the cost savings would be. From what I can determine it is anywhere from $900-2400 p/year. 

I do intend to hold onto the property long term 10-15 years maybe longer but by my calculations it could take that long to recover the cost. 

The only real pros that I can think of are 1) that I will have the ability to control it remotely, which could add to my savings and 2) the unit will need replaced eventually anyway. 

Thoughts? Anyone have experience making this switch? was it worth it?