Since the May update- my battery life has gone to heck. In 2 hours with no use- it drains 10 %. If I am driving on a high way or in an area where there is no wifi my battery will pretty much drain completely. Prior the life was pretty good. I am beyond frustrated. I hate my phone now where before I loved it. I am contemplating a factory reset but dread the whole personalizing part again.
What type of phone do you have? Many people who have had battery drain problems after updating to a new OS have been able to solve it by clearing the phone's cache. Before you resort to a factory reset try clearing the cache. If you resort to a factory reset whose to say you will not just repeat the step that got you to this point, and have the problem again? Its better to find the cause of the problem, so you can eliminate it and know how to keep from having the issue reoccur. Linked below is a walk-though on how to do a phone cache clear for an HTC One. If you have a different phone model you may have to do some research to see how to get to that phone's clear cache area.
In addition I recommend checking what apps you have running, and disabling any you don't use, nor plan to use. Here are some steps you can use to check what's using your battery, how to disable them, and a few tips on managing your apps (like closing them once you're done with them instead of leaving them running in the background). This one is based on the setup of an HTC One m8, so if you have a different phone some of the menus may be different.