&gt; All the web browsers used their default configuration, without any add-ons or toolbars installed.<p>My raw, untested guess is that using Firefox with some strict adblocking&#x2F;flashblocking etc. tools might reduce its power usage due to less HTTP requests, less CPU&#x2F;GPU time wasted  (though OTOH the add-ons may increase the CPU load to do their job, so it&#x27;s non-obvious).