Here's my little experiment:
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Fairphone 4, brand new, totally stock Fairphone OS, a few resource-light apps installed, light use for a week: 23 hours of use time from 100% to 20% battery on average.
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Wiped the same Fairphone 4 after a week, installed CalyxOS (deGoogled Android), reinstalled the exact same apps and used the phone the exact same way for a week (I still do in fact...): 44 hours of uptime on average.
I know with 100% certainty that literally the only difference between week #1 and week #2 was that the phone didn't spend its time constantly reading the sensors and sending surveillance data to the mothership.
So there ya go: even if you're mad and you're a fan of Google's dystopia, the extra load on the system does come with a significant performance pricetag.