Mostly anecdotal. It comes up on Reddit pretty often [1], for example this [2] discussion. According to this [3] article, OS X will actually warn about Chrome using too much power, though I haven't seen or heard about that personally.

[1] http://www.reddit.com/user/5HT-2a/m/machelp/search?q=Chrome+...

[2] http://www.reddit.com/r/mac/comments/2d2lim/a_thoughtwarning....

[3] http://www.forbes.com/sites/ianmorris/2014/07/21/google-will...

I'm not sure of any official tests, but I often keep Activity Monitor open, and I've noticed Chrome using on average 2x more CPU. Plus, that's excluding the occasional "Google Chrome Helper" that tries to use 95+% of the CPU randomly (even when the app is in the background).

Not that I'm claiming that this is proof that Safari is better than Chrome, but in my experience it uses a fraction of the CPU and gets the same job done.