Why is my iPhone 16 Pro battery draining so quickly?

I just bought my iPhone 16 pro yesterday and when I went to Settings->Battery under Insights and Suggestions there was note about Ongoing Device Setup informing me that background setup work is ongoing and battery life will improve once finished.

So like Jeff Donald says, give it a week.

This is normal. When an iPhone is new the battery needs to charge a few times to reach maximum capacity. New iPhones also need to sync a lot of data and also backup to iCloud, which may require more syncing if other devices such as iPads or Macs are involved. It also needs to index all the data to speed up operations such as search. Lastly, you probably updated to iOS 18.1 which requires installing Apple Intelligence and AI is busy learning about your other apps etc. Give it a week to settle in and then let’s revisit your battery consumption.

If you don’t want to accept our advice then schedule a visit to an Apple Store or authorized Apple service provider for examination.