Powell - on loan from Manchester United - re-established the lead early in the second half, and it would prove sufficient in earning victory for the Latics.
The hosts enjoyed much of the possession throughout the opening stages without penetrating the Town defence.
They would soon find a breakthrough, though. Ben Watson's floating corner was found by the head of Leon Barnett, who rise highest to thump home the opening goal.
Huddersfield responded well to the deficit and nearly provided the perfect riposte, only for Adam Hammill to see his goal-bound effort deflected narrowly wide off Barnett.
Town soon saw their dominance rewarded, though, as Oliver Norwood equalised in the dying stages of the first half via a Ryan Shotton deflection.
Nevertheless, Coyle's side forced the issue in the second half and soon saw their dominance pay off.
Powell wriggled into space, before thumping past Alex Smithies in the Huddersfield goal to earn all three points for the Latics.