Moore, the reigning world champion, was in her third straight NZ final after winning the inaugural event in 2010 and being runner-up last year.
"I just let a couple of waves go under my priority," said Moore, who sits third in the ratings.
"I didn't think they'd offer that much, but Steph (Gilmore) did a really good job."
Local favourite Paige Hareb finished equal third after losing to Gilmore in a tight semi-final 16.44 to 14.07.
Hareb led for the majority of the heat until Gilmore caught one of the best waves of the day, pulled in to a clean barrel and punctuated the ride with two massive turns.
"You get pretty pumped having the support of the hometown crowd," Hareb said after equalling her best result on the world tour and climbing to seventh in the ratings.
"That one bomb wave came through and Steph (Gilmore) happened to have priority at the time. I was just left sitting out the back watching her rip it apart all the way to the beach."
The other semi-final was tighter still as Moore downed American Lakey Peterson 12.93 to 11.92.
-AAP