Since the 4.3 update I have had terrible battery life.

Before the update I could go a full day from the morning I unplugged until bedtime (about 16 hours), and still have 10-20% left. Of course if I played a lot of games, GPS navigation, videos, etc. this wasn't the case, but in general my daily routine allowed me a full day of use without having to plug in.

Immediately after the update that dropped drasticaly. I could barely make it home from work before my battery died completely (about 9-10 hours after unplugging in the morning). Even with power saver on and every other trick to extend battery life I could barely make it home without having to plugin. My wife also has an HTC One, and had the same problem right after the update.

After reading through various forum posts and many google searches I found that I wasn't the only one with this problem, and it looks like HTC is finally acknowledging the problem and is working on a fix.

One thing I found is some people reporting some success by doing a factory reset. However others reported that a reset didn't help them. I figured it was worth a shot and I went ahead and did a hard reset. This is different from a factory reset through the settings menu, it's done through recovery by holding the volume down and power buttons to turn the phone on (google "hard reset" for more details). After doing the hard reset my battery life has improved drastically, and after 1 full day of use and a half day (today) I feel like it's back to pre-4.3 performance. I benchmarked against my wife's phone and my battery is outperforming hers by a long shot. I'll be doing a hard reset on her phone tonight as well.

So I think some of the people reporting no success after a reset may have been simply doing a factory reset through settings. There's a difference between a hard reset and a factory reset, but I won't go into the details here.

Anyway, if any of you are having this issue it might be worth giving it a shot. I just wanted to share my experience and offer a possible solution. I've heard of other issues people are having post-4.3, and this may help with those as well (I have no idea really, since this was the only issue I had after the update).

TL;DR Shitty battery life after 4.3 update. Hard reset (not factory reset) and my phone kicks ass again.