Google Play list the permissions the app needs when you donwload the Millheat app, but it can give a slightly skewed picture of the information actually being used as they have quite broad categories. Below is the screenshot you will find when donwloading the app:
What does the Millheat app actually access?
Photos/Media/Files: The app needs to access the files on the phone, so that the app can be installed on your Android device. Photos/Media is not being accessed.
WiFi connection information: The app needs this permission in order to connect your Mill WiFi devices to your WiFi
Device ID & call information: Google Play needs the Device ID in order for you to successfully download and install the app. Call information is not being accessed.