Big Sur upgrade - BIG battery drain

I just upgraded to Big Sur on my MacAir. I resisted for a while because these system upgrades ALWAYS causes problems and lo and behold - now my battery life has been DECIMATED. I used to get at least 6-8 hours on a charge. Now the battery is at 52% after just a half hour of simply answering emails What can I do. This has just rendered my laptop useless because I mostly use it remotely. Can I restore the previous system?