We were excited to see Google Now finally make its way to iOS, but it didn't come without problems. Many users report excessive battery drain due to location reporting. Fortunately, Cult of Mac offers a solution.
Here's the solution:
Hopefully the excessive battery drain be fixed sooner rather than later, then, but you don't need to stop using Google Now completely until that time comes. Instead, you can turn off location reporting from within the Privacy section of the app’s settings -- just hit the little cog in the top right corner. This will disable the features that rely on location information, such as live traffic reporting, but it won't kill Google Now completely.
Since this solution requires compromise, we'll hopefully see an update to the app in the near future that will allow Google Now to function fully without siphoning the life from your iDevice's battery.