Spotlight is that awesome little feature that sends all the breaking news to our phones the moment it gets reported. It's pretty much a necessity in this day and age and being first with the news allows you to stay on top of important conversations. The tough thing about Spotlight is that it draws from a number of sources in order to deliver your news. It's constantly working in the background and eating up a lot of battery life in the process.
The good news is that you don't have to turn off Spotlight completely. If you go to Settings > General > Spotlight Search you'll see that you can just limit some of the apps that are providing data to Spotlight. Once these have been limited, you'll notice a difference in your battery life almost immediately.