Microsoft's browser energy efficiency report needs a caveat.

Have a look-see at this report commissioned by Microsoft, which suggests that IE is more energy efficient than Chrome and Firefox.

Too bad they weren't consistent in how they updated the IE and FF browsers but not the Chrome browser, midway through testing:

Chrome 26.0.1410.64 (April 9);
IE 10.0.9200.16540 (April 9);
IE 10.0.9200.16580 (May 15);
FF 20.0.1.4847 (April 11);
FF 21.0.0.4879 (May 14).

For reference (stable) Chrome 27.0.1453.93 was released May 21.

Now, maybe IE 10 is more energy-efficient, but we won't really know if it was a fair test because Microsoft's browser was updated midway but Chrome's update wasn't included.  Timing issues may have been the reason, but the report wasn't released until today, and testing doesn't exactly take a day.