I am looking for advice on an electric tankless water heater for a two bedroom, one large full bath house with a dishwasher and clothes washer. No gas available, only electric, and this is NEW construction not a remodel. The 3/4″ inlet and outlet are in place as seen here in this photo.

Is it worth getting a tankless or should I stick with the tank? I previously posted this message and didn’t get any conclusive statements on which way to go. What size would I need? 100 amp? How many GPM would this small house need.

If you have to use electric, then the tank-less is the way to go. Keep in mind that there is a bit more lag between hot and cold and some put a small 120 VAC 5 gallon water heater under the kitchen sink to make up for this. This small electric addition seldom comes on as the hot water from the main supply passes through it and keeps it heated. This is also true in baths that are some distance from the primary source of hot water.

I have a similar question. We currently have an ancient gas water heater (tank) and because of the extensive shut-off system the previous owner put in the run from the tank to the kitchen is about 80 feet. We want to put in an electric under the counter tankless water heater to service only the kitchen, electric so we don’t have to run a gas line or go through the foundation for venting as our kitchen is below grade. Then we want to install a gas tankless water heater to service two bathrooms and laundry room. How do we figure out what size? Oh, most days there are just the two of us although more on weekends. We have a HE washer that is used mainly on the cold setting with 1 – 2 loads of hot wash per month.

My rule of thumb is “you can always use less of an over sized unit but you can’t use more of a unit that is too small.” These units automatically adjust the flame to match the water/temp flow rate. So a large unit will use no more energy than a small unit. If you have doubts, go big.

I tried an electric tankless water heater and was not pleased with the results. It was a 60amp unit and was rated to handle my whole house. It provided hot water that flucuated in temperature. I could hold my hand under the running tap in the kitchen and feel the changes in temperature; the same happened while showering – not fun [:O] . I ended up reverting back to an traditional 55 gallon electric water heater and have been pleased with the change.

There is no such thing as a 60 amp tankless water heater that would supply a “whole house” IMHO. That would be one of the smaller units, the larger whole house units might use 3x60x240vac.

Anyone wanting to look at electric tankless, should check out Stiebel Eltron & anyone wanting a gas or propane unit can’t do better than Takagi. Both of these companies have been building these thing for over 50 years and my research (which was extensive) brought me to Stiebel Eltron as the best electric unit available and Takagi as the top maker of gas/propane units. I opted for the Takagi TK3OS and it works flawlessly.

Buying a top of the line unit will save the most money over the long haul.