According to Neon John :
No. A thermostat is an on-off switch. As long as the room temperature is lower
than the thermostat's setpoint, it's on. When the room temperature reaches the
setpoint, it turns off. That's all.

Not quite. Technically a heat pump thermostat is a 3 state device, off,
refrigeration heat and resistance heat. Anyway,

Nit-pick: four state: off, refrigeration/heat, defrost (self
nitpick: via controller) and supplementary heat.

The supplementary heat doesn't _have_ to be resistive. Ours (in
a previous house) wasn't. If we go HP again, it won't be.

Really smart thermostats without outside temperature sensors combined with
multi-stage heating/cooling units, tune themselves to both inside and outside
temperature. I had that setup in my restaurant. It was remarkable how
my power bill
dropped when I installed that combo in place of the two single stage heat pumps.

Ours (with gas backup) had two sensors. I don't think it did a lot of
smarts with them, but it was remarkable how low the heating/gas bill
was, even in the great white north.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.