In response to a question today about how the Zune's battery life is affected by its wireless capability, I asked Microsoft for the official word on this topic.

The answer: Using Zune's WiFi radio shortens the battery life by an hour or two, or more depending on how much you use the wireless feature.

Zune spokeswoman Katy Gentes just told me via e-mail that the team is "working hard to minimize the impact of wireless so the difference in battery life for wireless on v. off is relatively minimal. The team has said it's looking at up to 13 hours of audio and 4 of video with wireless off. Wireless will probably shave an hour or two off that number for audio with a comparable ratio for video, but we're still testing so I can't confirm final numbers. Of course if you're continuously sending music during that time that will impact battery life as well."

So if you share some music with a Zune, the device should play for 11 or 12 hours on a charge. If you share a lot of music with your pals, you may want to ask for some electricity in return.

It's not an apples to apples comparison, so to speak, since the iPod doesn't have a wireless radio, but Apple claims its 30 gigabyte model has up to 14 hours of battery life playing music and up to 3.5 hours playing video.