[engi_nerd]

You have a point -- I don't know for sure, but my extremely high electricity bills (even during two relatively mild months) are my reason for believing that the Nest was activating the emergency heat.

EDIT: corrected that whole last sentence. It made no sense.

[ckinnan]

We had the same issue and had a pro service call, in our situation the Nest was calling for emergency heat.

[engi_nerd]

I wasn't willing to pay more money for a professional service call. I was hot and angry and frustrated. I de-installed the units and hooked up the old Honeywells.