How to fix battery drain on iOS 14.7

I'm posting this in the hope that it may help someone else.

My iPhone X has suffered badly from battery drain since iOS 14.6 and it continued on 14.7.1. The phone would hit red somewhere between 1200-1400h each day after only very, very light use and only while on wifi. And this was with a brand new battery, installed by Apple in January 2021.

In the end I decided to restore the phone to factory settings, having first followed the various steps needed before such a move, such as backing up to the computer and to iCloud, backing up WhatsApp's message history both to iCloud and within the app. unlinking my Apple Watch etc.

Then I decided to install apps on a "need basis" by which I mean that I would only install an app if I found myself at any given point to 'reach for' that app. The result is a much leaner (and faster) phone.

The first two days after the reset continued with poor battery performance, likely due to the behind-the-scenes indexing. But on the third day, which was yesterday, I saw major improvements. At bedtime yesterday it was still at 40% after quite heavy use having streamed music from my home server for several hours, a lot of time on Instagram and Flickr and some FaceTime calling. Today the phone has continued to be rock solid battery-wise.

I don't know if the poor battery performance was due to one or several apps that were not updated to play well with iOS 14.6 and .7 or if it simply was a result of a bogged-down phone to which I had just added apps over the last 3+ years. Or if it was due to some bad design flaw in these two iOS versions which made them incapable of operating effectively regardless of the phone's app configuration.

But the difference after the admittedly somewhat tedious factory reset is incredible. It's as if the phone is only sipping energy from the battery, as opposed to literally gulping it down like there was no tomorrow.

I hope this helps someone.

Best

Philip