I recently moved everything from my iPhone 15 Pro to a new iPhone 16, and the new phone feels unusually sluggish. Animations are choppy and the frame rate seems low, almost like Low Power Mode is enabled. The transfer was completed about 20 hours ago, and I left the phone switched on and charging overnight while connected to Wi-Fi. iCloud appears to have finished syncing.
During setup, the phone initially had trouble connecting to Apple's services and rejected my Apple ID login, but restarting fixed that. I also used to be part of a family Apple account before creating my current account. Some apps that had originally been downloaded with the old account appeared greyed out after the transfer, although I was able to reinstall them.
Could the account history or transfer have caused this performance problem, or is there another explanation or fix? I'm keeping my old iPhone 15 Pro active until I know the new phone is working properly.
2 Answers
There’s also a hardware difference that can make this feel much worse than expected: the iPhone 15 Pro has a ProMotion display with a refresh rate up to 120Hz, while the regular iPhone 16 uses a 60Hz display. Scrolling and animations can therefore look noticeably less fluid even when the phone is working normally. It shouldn’t feel genuinely frozen or unresponsive, but the difference can resemble Low Power Mode if you’re used to the 15 Pro.
A new phone can feel slow for a while after setup because iOS is still indexing Photos, restoring app data, and completing other background tasks. Keep it connected to Wi-Fi and power, then restart it once syncing has definitely finished. The old Apple Account probably isn’t responsible for the low frame rate. Apps that were originally downloaded under that account may appear unavailable because your current account doesn’t own them, so reinstalling them with the account you use now is the usual solution. Keep the 15 Pro untouched until you’re satisfied everything has transferred correctly.
It had already been set up for about 20 hours and was left charging overnight, so I’m not sure whether background indexing alone explains how sluggish it feels.
I didn’t realize the refresh-rate difference might be that noticeable. It really does look like my old phone had battery saving enabled, so that could be part of what I’m seeing.