> I work at Nest and it may be a little unclear at the moment (we're working on it), but The Nest API does not guarantee that if you send an ETA of 15 minutes (docs: https://developer.nest.com/documentation/eta-guide), the home will heat to the appropriate level in 15 minutes. It's actually filtered through our algorithms to determine the best course of action to not waste energy but also provide the appropriate level of comfort.

So you're accepting the ETA request not as a demand to obtain a certain temperature, but as a request, and then still taking utility demand information into account. Excellent.