I've been having the same issue on my MacBook Pro (15-inch, 2018) since I updated to macOS Big Sur 11.1 beta 2: the "powerd" process uses more than 100% of the CPU (usually about 104%), and neither quitting it manually nor restarting makes a difference. Thankfully, YukonJJR's trick with setting a schedule in the Battery pane in System Preferences seems to have worked. When there's no schedule enabled, the following messages appear multiple times per second in Console:
Process powerd.899 TimedOut InternalPreventSleep "com.apple.powermanagement.wakeschedule" age:00:00:05 id:55834610560 [System: DeclUser kDisp]
Wake timer expired for com.apple.alarm
(I found these messages by filtering the log with a search for "powerd"; it's possible that I missed some other messages that didn't include the string "powerd".)
Once a schedule is enabled, the messages no longer appear. For what it's worth, only a "Start up or wake" schedule works; "Sleep", "Restart", and "Shut down" schedules don't seem to do anything.
I would file a feedback report, but the Feedback Assistant server is down right now. I just submitted a feedback report ("FB8929860").