On Sep 17, 4:09 pm, roperman wrote:

My friend says this won't save any energy, because warming
up the hot water tank from a low temperature will take more
energy than heating it up throughout the day, where the
temp differential is lower.

Jay

No it won't.

See Chris's reply.

Your system will operate at higher efficiency when:
a. It runs for a single long period rather than a multitude of
short periods
b. It heats cooler water

-J