Few days back, we posted results of benchmarking tests done by PC Mag on Windows 7, Vista and XP. Results were equally divided between Windows 7 and XP in the six tests, as Windows 7 came on top in 3 and XP won 3. Vista didn’t win a single test. All the tests done by PC Mag were performance based and none measured the impact of the OS on the battery life. Well, now many tech websites have posted battery life comparison between XP and Windows 7. And the results are unanimous, XP trounces Windows 7 in every battery life test.

In battery life tests done by website Laptop on netbooks including Toshiba mini NB205, Asus Eee PC 1008HA and HP Mini 311, Windows 7 on average offered 47 minutes less than Windows XP running on the same netbooks.

Another website Liliputing tested battery life on two virtually identical netbooks: an Asus Eee PC 1008HA with Windows 7 and one with Windows XP. The website found that the netbooks with Windows 7 ran for about an hour less than the Eee PC 1008HA with Windows XP. Similarly, the website found that battery life on Toshiba NB205 also decreased when running Windows 7 in place of Windows XP.

jkOnTheRun also got same results when they ran Battery Eater test on Toshiba NB205. Test on Windows XP yielded minimum runtime of 5 hours and 50 minutes, whereas, Windows 7 yielded 5 hours 15 minutes.

On average Windows 7 offers 10 percent less battery life when compared to Vista on netbooks. And it’s not just XP that has better battery life than Windows 7, Mac OS X Snow Leopard also has higher battery life when compared to Windows 7. CNET tested battery life of a MacBook Pro running the two operating systems. Battery lasted 111 minutes on Mac OS X, whereas it lasted only 77 minutes with Windows 7.

Overall, XP offers better battery life than Windows 7, but Windows 7 has better battery life than Vista. As on average Vista showed 25 percent decrease (when it was released in 2007) in battery life when compared to XP.