iPhone 5 - Battery Life Problem on 3G.

I have an iPhone 5 16GB (Launch Model).

I don't live in a 3G area at home so I use WiFi. But when I go to work in a 3G area.

My iPhone's battery life decrease so quickly while on 3G. At work I am using it for Facebook and Instagram occasionally using it.

So from a fully charged iPhone at 9am to 5pm usually my iPhone will be at about 3% before getting home around.

While I had my iPhone 3GS I lived in a 3G area 24/7 and the battery was never that bad.

Is it something wrong with my phone, or is it me being worried?

Ross