So I have a Rheem #heatPump water heater. Take a look at the change in trends from last year (dark green) and this year (light green). That big spike in November is when a sensor went real bad and the heat pump portion stopped functioning. It took a few months of electric bills before I noticed the continually higher usage and checked around to root out a cause.

So Rheem sent me a free replacement sensor, two in fact so I have another spare, and I got that fixed. I also took the opportunity to put in a hot water mixing valve so with the idea that I could set the tank temp extra high through the day and use just the heat pump portion then bring that max temp back down in the evening and let that hotter water carry the family through the evening.

Utilizing #HomeAssistant and an air temperature sensor I set the tank max temp to high when air temperature was above average for some past period and then to set to low otherwise. By the looks of it it seems to have cut our energy usage down quite a bit.