Do you by any chance live in a place with really high temperatures the past week? London UK for example has been over 30 degrees and both my macbook and iphone batteries last significantly less.
As it happens for me in London also I haven't noticed a drop in battery performance, but then my stamina has been knocked and so I may not have been working my M1 as hard as usual...
Only reason I’ve noticed is cause my phone doesn’t last throughout the day as it used to do a week ago, and my usage according to “screen time” is “down 14% since last week”. But of course this isn’t anecdotal evidence at best.
Could have been it. I work and live in Thailand so it’s always hot, but might have Ben sitting outside more