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If you mean will it get the same battery performance as the OS it shipped with originally, no. iOS 14 will decrease your screen on time but how much will depend on the condition of your battery. If your battery is in good condition the difference is acceptable considering the added features in my opinion..
 
For my not terribly old but definitely aging XS, battery life has been much worse on iOS 14.
 
I updated my iPhone SE original and my iPad 6 to iOS 14.3. It seems to me that the battery life has improved; not significantly, but adequately better.
 
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