Watch battery draining after update.

A heavy battery load is pretty normal for a day or two after updates. The install process you watched is only half the job. It will continue in the background, cleaning up the file system and reindexing which all add work which uses battery power.

I suggest give it about 2 days to settle down (with extra charging if necessary) then Force Restart (reboot) your Apple Watch and see how it is behaving.

Restart Apple Watch - Apple Support

I had the same issue and took mine to the apple store. Everything was fine with my watch. It turns out it was the 3rd party apps that I had installed for watch faces. I deleted those apps then I unpaired my watch and reset it and paired it as new watch. That took care of it and now its back to normal .

Mine started after the latest update. I will call Apple support tomorrow. Mine charge doesn’t even last until noon. It started at the exact time I took the update

Did this work?

I will try that! Thank you. I did download new watch faces but I am not using them. Thank you 🙏