Figured it was heatpump but no HVAC was running. This just popped up and is crazy consistent. I’m stumped.
The lack of a significant motor-start peak suggests it is not a large induction motor.
The periodic pattern suggests something is maintaining temperature against a constant-rate thermal flux.
Check to see if you might have left an oven turned on, last evening.
This pattern started last week and has been pretty consistent after that. I did double check over and the dehumidifier because I thought those both were likely.
Do you have a hybrid water heater?