To get information about how much battery your watch uses, open the Wear OS by Google app on your phone and go to Advanced settings and select Watch battery.
The data is available only if you have the watch Connected to the app. If you cannot connect the two, click here for more information. 
Note: Your battery info resets each time your watch is fully charged. The battery usage for apps and watch faces is an estimate, and not guaranteed to be accurate. Watch faces may use more battery than estimated.
In case you are sending your watch to our service center, please take a screenshot of the information displayed on your phone and attach it to the Online Service Request.
Our technicians will need this information to be able to analyze your watch.