Dom. hot water reset?

Chuck_7

Before I go through the effort of figuring it out for myself - a client asked about reseting (turning off) the domestic water heater at night. In this case it is for a laundry for an apartment complex. It would be off for 9 hours. The question is - would the savings pay for the time clock or what ever we use to control it?
The 75 gallon water heater will be direct vent so I think the heat exchanger loss would be minimal (as opposed to a natural fired where the heat loss would be significant).
I could try to calc. the heat loss(savings). The most/only useful problem I remember from school was a heat transfer calculation to determine if a beer can would cool more quickly on it's side or standing straight up. This would be similar.

jp_2

significant heat loss

I've heard this many times about traditional HW heater having big losses.
last year my 30 gal sat in the basement, no heat. the plumbing leaked a little and left ice on the floor, basement stayed below 30F most of winter. I kept the tank around 115F, used little water cause it was too cold to shower. cost me about 9 Cubic feet per month. so much for huge stack losses and jacket losses. I did use about 4 gal/day.