Significant battery drain after update to iOS 6.1 (iPhone 5 and iPhone 4S)

Try deleting your email accounts and then reading them.

The two issues are definitely related. Your phone is hot because the CPU just started running overtime.

The high CPU activity is the culprit to your battery draining.

Others found email to be the software cause.

Start by removing all email accounts including the iCloud one.

Wait an hour and see if your battery is still draining. Hopefully you'll see the drain has significantly improved.

Add your email back if you have multiple accounts then add one at a time and wait an hour between each to make sure they are each adding without causing battery drain.

Also there are opinions of network settings causing the issue as well.

Try resetting network settings it might further improve.

Hope this helps.

I noticed the same problem,fixed by the following steps:

- erase all data's under settings,general,erase

- use my PC(not my Mac) for restore

- NOT restored from an old backup

- after that was complete, just sync as new,add all emails address manually,and photos and all...

- battery life improved by 50%

Hope this will help out.

Good luck