The song doesn't use power chords but if you are playing it on guitar it sounds better 
just playing the root notes. Basically it's

Verse and Bridge:

A Bb A Bb A A A Bb A

You can figure out the rhythm.

The chorus is

A Ab A Bb A Ab A repeated 
over again

That's pretty much it for the chords.

Lame song, I know, but catchy and chicks dig it which is why we all play guitar in the 
place.