On Demand supplement hot water

[Ron Van]

Isn't recirculation as wasteful as just purging the pipe as I do.

The hot water circulators waste a little energy used to heat the water since the water cools while it’s being pumped around your house but not a tremendous amount because the water is still warm when it returns to the tank. The main thing (especially for Western states) is that is doesn’t waste water.

 

[Hamberg]

Most of them don't list inlet temperatures, so I have written to customer/technical support.

Exactly my point, think you are looking for something that does not exist!?

 

[Eddie_T]

The hot water circulators waste a little energy used to heat the water since the water cools while it’s being pumped around your house but not a tremendous amount because the water is still warm when it returns to the tank. The main thing (especially for Western states) is that is doesn’t waste water.

Actually the heat loss would be greater as t would be a continuing loss rather than just replacing the 1.5 gallons in the pipe.

 

[Eddie_T]

Since demand heaters don't have a tank the thermostat mainly prevents overheating. Flow turns on the element and some raise temperature (if you want higher than 120°) by restricting flow. They may not work properly in series with a tank heater. BTW I dunno I am only guessing.