Reports that Google Now drains battery life are incorrect. We understand people’s concern about seeing the Location Services icon stay on when they use Google Now. Many apps that keep the icon on actually do drain the phone’s battery because they require very accurate location. (For example a navigation app has to run your GPS all the time to keep you from missing your turn.)
Google explained that Now is “built very differently” than other apps that utilize Location Services by using “cell towers and wifi hot spots for much lower battery impact.”
Google’s response continues by noting it didn’t receive any reports of battery drain during its extensive month of testing the feature on iOS and encouraged users to contact them if they continue to see a problem:
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We extensively tested Google Now on iOS for months and didn’t see reports of significant battery impact — we would encourage you to try it in the Google Search app for a few days and we don’t expect you to see significant impact on your battery. If you are seeing a problem, please do tell us (just tap feedback in the app settings). We take user feedback very seriously.