Hope you have lots of excess electrical capacity available, those things make extraordinary current demands on the system.

Steve

 

Sounds like it's far easier to install tankless in new homes than to retrofit old homes. Is that where all these tankless units are going to, new construction?

I stopped looking at them when flue size became an issue. The local plumber says our water makes them scale up pretty quick too. The heat exchangers don't like really hard water.

 

80-90% of my sales are retrofit into older homes. Since the unit I sell is direct vent as long as you can get resonable close to a outside wall or the roof you can put one in

 

I have had a tank-less hot water heater (Aqua-star, now owned by Bosch) for more than ten years now and my father-in-law has had the same model for more than 17 years. I did not have any issue venting my unit, I just vented it with single wall galvanized vent pipe to the connection that my old gas hot water heater had used. We do have issues occasionally with the burner cutting out while we are calling for hot water. The reason for this is the flame only burns when it senses flow through it and are house has very low water pressure (30psi where it enters our house). This problem would not be an issue if you have decent water pressure (40+ psi). We had to convert all our faucets to one's that have separate ***** for cold and hot water. I also turned down the heat setting on the water heater so we only need to crack open the cold water a little when we are taking a shower. This helps maintain the best flow possible through the water heater, so the flame does not cut out. I'm currently in the process of adding a water pressure booster set up in our house to eliminate the low water pressure problem. Even with the issues I've had, I would still buy another tank-less water heater (gas) in the future. BTW my house is over 138 years old, but all the plumbing has been updated, including a new 1" copper pipe to the water main at the street.

 

So far my research has yielded that my gas feed line and vent
will need upgrading.
So now I am looking into electric,or hybrid tankless.

 

Consumer Reports just ran an article on tankless heaters; sounds like groundwater temp, no hot water at low flow, and initial cost are the main concerns.

Steve

 

I had posted earlier that my tankless water heater would sometimes shut off while I was calling for hot water due to low water pressure (flow). Well this weekend I installed a water pressure booster system I put together with a 3/4HP pump with pressure switch, 20-gallon diaphragm tank, 3 shut off valves, and various copper fittings and pipe. The results were great! We only had 30psi water pressure from our gravity fed town water supply and we now have 55psi with this setup. No more cold low flow showers and we have plenty of water pressure at all the taps. I found a brand new booster pump at a garage sale for $75, which had a small 2 gallon diaphragm tank. I felt that the 2-gallon diaphragm tank was too small, so I bought a 20 gallon diaphragm tank from Lowes for ~$150. I already had the copper pipe I needed and some of the copper fittings, but I needed to buy all the valves and more copper fittings (~ $150). So ~ $375 and the better part of the weekend I finally fixed an issue that has been plaguing us at our house for more than 20 years.

 

Do you have teenagers or soon to be teenagers? The gas / electric bills will eat you alive. Better to run out of hot water, even though about putting a smaller water heater in or rigging up something to slowly start to close off the hot water after the bath light had been on for twenty minutes.

 

A guy who built a new house near me installed a gas fired tankless water heater on the outside of the house. That way he was able to minimize the flue requirement.