The browser power meter displays the minimum setTimeout callback interval which indicates the browsers impact on power consumption. The shorter the interval, the less time the CPU can enter longer sleep states therefore consuming more power and impacting battery life.
The web platform allows for periodic callbacks via window.setTimeout() and window.setInterval(). In order to achieve small minimum timeouts, most mobile browser vendors decrease the timer resolution from the default 15.6ms to 4ms which comes at the cost of power consumption. IE9 mobile does not lower the system timer resolution in order to achieve a longer battery life while browsing the web.
Plese see the desktop version of this demo for more information.