Hi, I have exactly the same issue on my iPad Air 4 under iOS 15 and I have tried everything since 2019 (on my iPad Air 2). I have also created a completely new iCloud account and there was no change. I loose 10% a day while doing nothing instead of 3/4% while iCloud disconnected. My wife's iPad does not have the issue and she has a Home access.

Have you tried to disconnect the Hue Bridge for a moment (at least 12 hours) ? And check if there is a difference of battery drain ?

I have reset my iPad Air. I have changed my Hue bridge. No change. I still have battery drain with Homekit. 7/8% a day. For the moment, I have made an automation which turns off Wifi every day at 23h30.... Useful when I do not use my iPad during 2 or 2 days, it prevents battery drain....

Hi, I have a brand new iPhone 14 Pro and experiencing bad battery performance... I reach 50% of battery usage within 3 hours of screen use instaed of 5hours. I have made a fresh install without iCloud backup and I'm upset with this issue not yet resolved after years ! What's wrong ? I don't know if Homekit is the root cause because I cannot proove it...