I see the discussion of scheduling, that was going to be my next question. Would I gain significant benefit in raising/lowering the set point to follow my TOU hours. This property is on a grandfathered E-6 rate. Currently it is set at 120 degrees, heat pump only 24 x 7. I'm limited to heat pump only until the electrical work is done.
If this home is not net zero on electricity use, then yes, you could set the heat pump only to run during E-6 plan off-peak rates to save money. But you may want to consider at least a couple things:
1)
Unit may forget schedule:
At least once a few months ago our HPWH just decided to forget the schedule and wife calls me at work to tell me she and our boys had cold showers. Was able to hop on my app and set things straight.
With rental tenants, that may be even more problematic. Might be nice to have a 240V inline switch that you can remote restart the unit if your run into that issue but can't get the app to resolve the problem.
2)
Temp set point may be insufficient:
A water temp set point 120°F may not be high enough in the setting of running the heat pump only during off-peak hours. To compensate for this, you can increase the set point to as high as 140°F, in theory. But I am not sure if there are legal implications, especially as this is a rental unit for setting temp >120°F. You may want to consider a mixing valve in that case.
In the summer, under our E-6 schedule, we set our 65G HPWH as low as 124°F. 4 occupants standard, each two showers a day + laundry and dishwasher. In peak winter (gets significantly colder here than the bay area but significantly warmer than most of the U.S.), set to ~130°F and as high as 136°F if guests staying with us. During winter, E-6 only has 3 hours a day that are not off-peak and only on week days, so that helps.