Graphs and temps for the last 2 days. The room with the hotwater heater is similar in temp to the blue temp line marked office.
Jan 15th
Jan 16th
So far this morning is hard to tell if it's a valid difference or not, the house was a bit hotter then the previous nights by about a degree. the hotwater heater kicked on at 1:07, 4:21 and 7:49 before regular water usage started at 10:22. So that is a little over 3 hours between reheats.