Energy efficiency does matter for small-scale stuff like mobile devices, and for medium-to-large-scale stuff like servers (unless money is no object). But yes,

Energy efficiency does matter for small-scale stuff like mobile devices, and for medium-to-large-scale stuff like servers (unless money is no object). But yes, it's not really all that important for something like AI research. Especially considering that at the rate AlphaGo has been improving,* by some time in the next year or two it should be able to beat Sedol running on a smartphone. *And yes, there's no guarantee it will continue improving at the same rate.