I have that annoying situation since Catalina.. I did the "disable notification" on System Preferences for Safari and it appears as it is working.. I will post more news here in 24 hours to be 100% sure. I will let te application running (which was the cause of saying Safari was using too much energy.. Apparently disabling Safari Notifications is the "cure" for that annoying banner..
in 24 hours from now I will post an update, certified update. (at least it is working not to displaying that banner!!)
EDIT: not working! (banner just appeard in less than 2 hours)
PS: This is absurd! if i have plenty of energy, plugged on the wall, just 1(one) message would be enough, since I have clicked the X to close it, the App should be ware that I AM AWARE! Hell..
If I want to keep it opened (tab or main windows) is because I need it to be opened, and the advice was done [by Safari] and acknowledged by myself!
No need to be displaying that banner AFTER I had acknowledged it!
Oh Hell!
Steve (Jobs) we all miss you! You would never let such a thing to exist the way it is existing with this kind of behavior