Here are the terms and conditions.[1]
Nest resells this program, without saying up front that it's about adjusting your thermostat for their advantage.[2]
The site will not work in private browsing mode - you get "Cookies are blocked. To continue, change your browser settings to allow third-party cookies and try again." Why it needs third party cookies is not clear. It's so Google.
What Nest tells users is this:
A Nest thermostat can help you use less energy by cooling your home in summer or heating your home in winter ahead of time and tweaking the temperature up to four degrees during the rush hour.
You’re in control. If you’re home, Nest won’t let the temperature become uncomfortable. You can change the temperature at any time.
The Nest site does show terms under Legal. No mention of "Nest won't let the temperature become uncomfortable" there, of course. [3]
"Under the program, your Utility notifies Google of the existence of a Rush Hour Rewards event, causing Google’s servers to remotely inform your Google Nest thermostat (“Nest Thermostat”) to automatically change the temperature setpoint in your home on that day, without any manual intervention by you."
[1] https://my.radiothermostat.com/rtcoa/terms/ercot/rtcoa-ercot...
[2] https://nest.com/energy-partners/texas/
[3] https://nest.com/legal/energy-partner/texas/