MacBook Air - MacBook Air & External USB HD

I'm switching computers from a macbook to a friend's macbook air. The macbook air is setup as new. I have time machine backups on an external hard drive that is powered by plugging into two (2) usb ports.

I know the macbook air only has one usb port, so I'm wondering: if I get a hub, and plug my hard drive into that, will there be enough power generated for the drive to function? Has anyone ever done this?

Alternatively, if that can't be done, how can I go about getting the macbook air setup via my time machine backups? Any ideas or suggestions are appreciated.

Thank You!