IMHO a whole-hou$$$e heat pump System running all year warrants either spare DCM (Flex sensors) or the purchase of an additional dedicated Sense monitor. The signature complexity of variable speed DC motors and a lot of pumps and electronics makes for very difficult detection. Even if Sense could manage 95% accuracy I’d still want ground truth from DCMs.
Hell, Nest or thermostat manufacturers, or dare I say HVAC manufacturers, should wise up and build Sense into their devices, or at least talk Sense like ecobee.
FYI: switching your thermostat to an ecobee could help …
And one last thought: I think the next big thing in device monitoring of heat pumps is going to be for refrigerant leak detection. The climate impact of leaking refrigerants is astounding and any form of early warning is very significant technology. Sense ground-truth data could well deduce a leak. My bet is we’ll see mandates in places like Berkeley and then soon-after, globally.