Tankless Water Heater Advice Needed

[Jeff Wisnia]

A friend who's facing replacement of a 60 gallon gas water heater asked me what I knew about electric tankless heaters.

The "family" is two adults living in a single family house in the Boston Area.

I've no firsthand experience with tankless heaters. The bit of stuff I've read leads me to believe that installing a whole house tankless unit as a replacement for their gas fired heater is very likely going to require increasing the capacity of the electric service to their house, along with the installation a new panel and heavier conductors from the panel to the tankless heater location.

The incoming water supply temperature around here gets into the low 40s during the winter, requiring a pretty powerful tankless heater in order to raise that to a comfortable temperature for showering, even with a low flow showerhead.

And, if one person is showering and the other starts the clothes washer and then decides to do the dishes, things could get coolish in the shower, huh?

I'm thinking they'll be needing at least a 125 amp 220v circuit for the heater, which will almost certainly necessitate the electrical changes mentioned above.

Comments from those in the know?

Jeff

[Pete C.]

Why would they not replace a gas tank type with a gas tankless type? Either way, the tankless type have lower standby losses than the tank type which may or may not matter much depending on the usage patterns and unit location where the lost standby heat goes.

I don't know what the various utility rates are in Boston, but I though I heard NU had like a 20% rate increase recently. Surely gas is cheaper especially if they already have gas service in place vs. needing to upgrade electric service.

Pete C.

[hallerb]

gas will require a large new gas line directly to the tankless and may require a new flue, all those BTUs have to go somewhere, the install will be expensive, tankless will require routinue maintence by qualified techniocians $$$ if the tankless quits working NO HOT WATER AT ALL, the costs will exceed the standby losses, the paayback exceeds the tankless warranty and expected life.....

a regular tank is a much better deal, if they complain about running out of water upgrade to a 50 or 75 gallon tank with a 75 thousand BTU burner, most regular tanks are half that, such a upgrade they will never run out of hot water, it will double their capacity:)

regular tanks standby losses helps heat the home in the winter

[Tim Smith]

You might also want to look into the smaller tankless heaters that serve a single fixture, instead of a whole-house heater. One for the kitchen sink, one for the washer, one for the shower, and one for the bathroom sink.

I'm not saying these are any good--just suggesting considering all options.

[hallerb]

Go with a standard GAS 75 or 100 gallon 75,000 BTU tank. If their existing tank is 35,000 BTU this will double the capacity.

Tankless on low flow like one fixture running slowly are often below the minimum trip level to turn on the burner or turn on the electric resulting in cold water for these applications.

Another thing a electric tankless or most gas tankless no electric means no hot water at all.

[George]

It depends, the good ones do a good job sensing flow and regulating temperature. Also the ignition is powered by electricity that is generated by the flowing water.

[Jackson]

Agreed - I can't think of any way that anything but a flame fired device is going to work for tankless hot water system north of the Mason Dixon. Most of the units I've seen that work well are gas, but the same basic principle has been in use with oil fired furnaces for many years. I wouldn't touch an electric tankless system, can't even think why they would make such a thing, even worse try to sell it in New England! Usually even an electric hot water tank can't keep up with one shower, how would a tankless unit do it?

Just my 2cents - FWIW.

[Jackson]

Guess he told you, Jeff! ;-)

[Jackson]

I don't know, I would seriously consider a GAS tankless though, but I've got a wood stove and live in redneck country.......