Kiwis Scott Dixon and Scott McLaughlin have fallen far short of their IndyCar championship aspirations, failing to push their claims in the season finale at Monterey, California.
Both took mathematical chances of claiming the crown into the Laguna Seca showdown, but were set on the backfoot in qualifying. Shooting for his seventh title, Dixon sat just 20 points behind Power, but started 13th on the grid.
With three wins under his belt in his second US season, former Supercars star McLaughlin was better placed at seventh in qualifying, sitting 41 points adrift overall, but as tyre strategy became an issue early in the 95 laps, neither were able to mount a serious challenge on the leaders.
McLaughlin finished sixth, almost a minute behind Palou, to finish fifth on the standings, while Dixon's 12th placing could not elevate him from third.
"We ultimately just didn't have the pace," said Dixon. "It was definitely a strange race in that we tried everything we could - we tried to short-stop, but kept coming out in traffic.
"We had one run there where our pace was as good as the leaders. Just frustrating that we couldn't bring what we needed today."
Defending champion Palou captured his first win of the season, beating American Josef Newgarden by 30 seconds - the biggest winning margin of the season.
The Spaniard is currently in a contractual dispute between his Chip Ganassi Racing team and McLaren Racing for next season.
Power had one hand on the trophy, when he secured his record 68th career pole position for the final race, with Newgarden starting at 25 on the grid, and ultimately did enough to finish third and cover his nearest rival.
