Board Thread:Questions and Answers/@comment-108.0.90.90-20140127044402/@comment-6053530-20140325071254

Answered in Dracoenergy comment section.

Yes, because the battle step ends after “Counterattack” and “Double Attack” abilities activate. This means "Counterattack" is considered to be part of the battle. Since the power bonus is granted until the end of the battle step, you get to keep the power during the counterattack.

Refer to page 4-5 of the detailed rules here for more information.