Constantly heating a whole tank of water all day long when nobody's home isn't efficient.


Depends on how efficient your tank is.

My entire heating system (which includes the hot water) is designed for efficiency: A computer-controlled variable temperature oil-fired boiler (made by Buderas) with six heating zones, a Riello burner, and outside air temperature monitoring to control boiler temperature. See attached photo.

My hot water tank holds 55 gallons, and is so thoroughly insulated (at least 6" of high density foam) that I cannot discern the slightest difference in temperature between the outside of that tank and any other surface in the room -- a room which (in the winter time) is kept at an ambient temperature of around 50 degrees.

However, I know what Bitt is saying -- it takes a long time for the hot water to go from that tank to the rear bathroom, a distance of over 70 feet as the pipes run, and of course when the hot water is not in use, the water in those pipes loses its heat, wasting the energy. In my case, the heat is not wasted for at least seven months out of the year, as it helps to heat the house.

tanstaafl.