DIYbanter - View Single Post - Converting from domestic (tank) to tankless water heater

Robert Gammon

wrote:

Changing from tank to tankless should not be particularly expensive if
the two heaters are the same fuel type. If you have an electric tank
type and install an electric tankless or have a gas tank type and
install a gas tankless.

WRONG!

Both the gas or electric tankless consume many times the fuel gas or
electric used by a tank type while they are operating.

figure a upgrade to 200 amps just for a electric tankless, plus a
second main for regular home power uses...

I agree with both assertions above.

tankless whole house hot water heaters are the largest single consumer
of energy in your house while they are running.

The difference for gas is 40,000 BTU input that runs several hours a day
to keep 40 gallons at 125F vs 198,000 BTU input that runs maybe 30
minutes a day.

And yes, an extra 200Amp circuit will have to be run from the local
utility JUST to supply the tankless Electric as so few of us will have
more than 200Amps already installed, much less as spare capacity. But
keep in mind 200Amps is for the largest of the tankless units. The
smaller ones can get away with 50 to 60Amps, and we MAY have the spare
capacity for that in our breaker panel.