Q. Subject: Nest thermostat 3rd generation
Is it OK to have it on the wall Shabbes. It lights up when you pass it. It is learning your schedule and adjusting itself accordingly.
A. Horav Shlomo Miller's Shlit'a opinion is that it is apparent that the many features that this thermostat contains are triggered by sensors that are turned on by someone passing by, or off when no one does. The fact that the sensors work faithfully and due to the significant savings in energy resulting, they are also desirable, has an effect on Halacha. This is a case of “p'sik reisha denicha lei” or the inevitable consequence of an action that one desires, therefore this thermostat should not be used on Shabbos.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a