A Google employee has taken to the Macworld forum to deny claims that Google Now for iOS is tough on battery life. There have been numerous reports that Google Now rapidly drains a device's battery, but this Google employee says these reports are "incorrect."
Many have blamed Google Now's Location Services, but Google counters this by saying the app is built differently to minimize the impact of Location Services. Instead of GPS, it relies on cell towers and WiFi hotspots. Reports claim that the Location Services arrow is displayed "permanently" after enabling Now and only goes away after deleting the Search app.
According to Google, who says they tested the Google Now for iOS app for months, they did not observe any significant battery drain. What qualifies as significant is up for argument.