[ashark]

I used to own a house equipped with a heat pump, and in heating mode the cheap-o thermostat would display "e heat". Maybe it's just common to use the same control circuit for that, that might otherwise be used for some sort of actual emergency heating device?

It just said "heat" when the furnace was on.

[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.

[maxerickson]

e-heat is the manual override to use the resistance heater in the heat pump (it also disables the heat pump part of the heat pump). It shouldn't normally be triggered.

I don't know anything about nest, maybe it displays that in other situations.