Iphone draining battery only on standby?

I have an Iphone 4S running on ios 7.0.4. It was at 40% last night and after having it on shuffle for about an hour and a half my battery was at 38% which seems normal. However, I charged it to 90% afterwards before going to sleep and woke up to my alarm 7 hours later to find it at 14%.

I'm downloading the latest software update and hoping it fixes the problem but I'm not sure if this is an issue deeper than that. What could cause a phone to only drain its battery while it's doing absolutely nothing?