If you open the Activity Monitor and see that a process called "google chrome helper" is using too much CPU, here's how I fixed it:
I went to Chrome settings/content settings/Plugins and selected Click To Play for all plugins. (The default is Run Automatically.)
This fixed my problem. Now you have to click whenever you want to run a youtube video or other plugins, but it's worth it. It stops those stupid Flash ads from loading, too, so that's an extra bonus.
I'm posting this because when I had the problem, I couldn't find any solutions at all.
reference : https://discussions.apple.com/thread/5572267