Hunter-Reay finished fourth Saturday to clinch his first career championship, overcoming defending champion Power's 17-point advantage coming into the final race of the season.
Power's bid to repeat as champion came to end when he spun out and crashed into the wall on lap 56. He managed only a few laps after that before he was forced to pull out, finishing in 24th place.
Hunter-Reay barely managed to avoid Power's accident.
Ed Carpenter claimed his second IndyCar victory with a first-place finish Saturday after passing Dario Franchitti for the lead on the final lap.
Scott Dixon came in third and Helio Castroneves claimed the fifth spot.