If Thunder Mountain {*} is in play, does Pikachu & Zekrom GX's "Tag Bolt GX" attack need 5 {L} attached or 6 {L} attached in order to get its bonus effect?

The base energy requirement of the attack is one {L} less for Thunder Mountain {*}, but it does not apply to the additional energy required for its bonus effect. You need 5 {L} attached in order to get the bonus when Thunder Mountain {*} is in play.

Relevant cards