iPhone 5S getting incredibly hot and high battery usage after iOS 8 update

My top battery usage is 'Messages (background activity)', or words to that effect at 25%... makes me wonder if under iOS8 there isn't some sort of re-indexing with the cloud that's taking place which is causing excessive activity...

If I can think back to my earlier new iOS experiences, I think it did feel like it took a 'day or two to settle down' - so, hopefully over the weekend I/we'll see things going back to normal.

Or else... let's hope for a quick iOS 8.01 release!

I'd prefer not to re-install, because that shouldn't have to be the case after installing the software,, but if Apple provides no solution, then I may have to.

If you used an over the air update to iOS8 a restore is exactly what you should do

It will install a full fresh installation of iOS8 rather than a "patch"

A lot can go wrong with an install, especially an OTA one. iTunes will pull down the full version, sometimes no matter what it can go wrong as there are a lot of system files to replace. Its always best to have no apps running in the background, have the device plugged in as well. I'm not sure its an Apple specific issues, this crops up a lot when a new OS comes along. It sounds like a runaway process, and maybe caused by a corrupt install. Next step is to try a clean install. Since not everyone's phone has this issue its more likely to be a corrupt install. If your phone behaves after a clean install then don't restore it from a backup and start from fresh.

I can only assume you are not a Windows user then, anything can go wrong with MS Windows and usually does

iOS can have the same issues

I updated 5 x iOS devices to iOS 8 all over the air and all faultless ,to my surprise

Turn off HANDOFF 😮

take it to an Apple store genius bar and get them to look at it ,it should be in warranty still or a couple of days out

Same issue. Fast battery drain, and hot iPhone. Some process is using the CPU a lot after updating to iOS 8. Battery usage shows Mail and lock screen as the most used battery, with 34% and 16% respectively. Even having the mail app not running. Apple iOS 8 should give a fast solution to this issue in a short time. It is really eating battery abnormally.

Did you try resetting your device ??? Just press the home and power button as long as the screen goes off, then again boot up... This may fix the problem

thanks did that already but no luck.

I got the same problem when I upgrade to iOS 8 over the air. Eventually I did the following steps and the problem seems to be gone.

1. Backup your iPhone using the latest version of iTunes. Mac or Windows should be no different.
2. Double check that your backup exists. On iTunes for Mac:
   iTunes > Preference > Device [tab] > check that your device name is on the list with the current date & time
3. Now that you are sure that all your content are backed up, go ahead and reset your iPhone
   Settings > General > Reset > Erase All Content and Settings
4. Wait until the phone is reset, plug the iPhone in to your computer again.
5. Select the option to restore your iPhone using the latest profile.
6. Let iTunes go through the process of backing up your settings and contents. It took about 2 hrs total for me.
7. That's it. You may have to re-download some content that is not part of iTunes.