I think you should look at your battery stats and other apps in your device before coming to conclusion. You mean Google Search, Google now is the sidebar thing you swipe from the left.
What you could do is logout of Google Now and disabling Google Search auto detect by going into it's Settings (tap hold on the home screen), you should have the option to turn off Google now in there, then go to Voice and uncheck "hot word detection".
I doubt it's the culprit to your battery problem, if it is the fault of a Google app likely it's something else like media scanner or google play services.
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