Originally Posted by John_Kunkel
Originally Posted by 340Cuda
I was very interested in one but found in a retrofit the cost the unit and the installation costs made them uneconomical. However my hot water heaters are inside mechanical closets inside the house.


Same here, the units I looked out required a minimum 3/4" line for natural gas and mine is 1/2" coming out of a concrete slab. Retrofit would be cost prohibitive but I like the concept.
The ones I looked at needed a different vent through the roof also. However I am with you I like the concept, just could not get the numbers to work.