My iPhone 14 battery seems to die way too soon

A decline of about 1% a month.....on average.....would be expected, so your battery is doing just fine. Some months, the battery might not decline at all, then drop 2% the next month. This is normal.

Although you see a reading of 90%, that might actually be 90.9%, but Apple always eliminates any tenths of a percent and rounds down.

If your battery declines to 80% in the one year warranty period, Apple will replace the battery at no charge.

Some simple math would project your battery to be in the 80% range in about 10 months or so from now.

Hello~ Your battery isn’t a problem until it’s at 80% or below. In fact your battery % is good. Click on below…

iPhone battery and performance

If the battery in your iPhone drains too quickly - Apple Support

~Katana-San~

Apple will replace it if it goes below 80% within the warranty period.

Hello again ~ You’re welcome.

~Katana-San~

Your iPhone’s battery health is expected to drop about 1% per month. After 9 months of use, you should indeed be at around 90-91%. You are correct in that there is a warranty for batteries that go below 80% health within a year, in which Apple will replace the battery for free. Note that all rechargeable batteries chemically degrade and that eventually we all have to replace the iPhone batteries. Don’t keep worrying about your battery health and just enjoy your iPhone.