This is a noob question im sure but i need an answer for it. Can powerchords determine the key a song is in? I know that you can usually (but not always) tell what key a song is in by the first note or chord that is played in a song, but what about power chords? I just didn't know since power chords technically aren't considered chords. Thanks for the help.
You take the notes in the power chords. For instance, if you have A5 C5 D5, the notes are A E C G D, which fit in the key of A minor, so that is A Minor.
Yea, by remaining neutral and not being maj/min, it leaves you open to many many key choices
^It depends on the other chords, though. For instance, my progression definately would not be A major, even though A5 has an ambiguous tonality.
people usually replace the diminished chord (II in minor, VII in major) with a regular power chord because it doesnt sound as abrasive in context. dont let that throw you off either.