What is an inverted power chord?

An inverted power chord is one where the 5th note is played higher than the root note.

For example, a regular power chord of G5 is played like this:
G D
3 5 x x x x

The G (root note) is played on 6th string, 3rd fret.
The D (fifth note) is played on the 5th string, 5th fret.

An "inverted" G5 power chord uses the same notes (G and D), but with the G played as the higher note of the pair.
- D G
x 5 5 x x x

In this case,
The D (fifth note) is played on the 5th string, 5th fret.
The G (root note) is played on 4th string, 5rd fret (an octave higher than regular)

If playing a 3-note power chord then both the G (root note) positions are used, thus:

G D G
3 5 5 x x x

It's all a little confusing for the beginner, but just remember... if it contains the root note and the fifth note and no other notes, then it's a power chord!

What is your favorite Power Chord song? . . -:
Power Chord A5
How to play a power chord of E (E5)Power Chord Trainer - RedPower Chord Trainer with instruction Leaflet