Ernster attended Northern Arizona University, and was a kicker, until punting his senior year. As a senior punter, he led the NCAADivision I-AA level, and the nation in average yards per punt, averaging 47.8 yards per punt. During his career at Northern Arizona University, he was a three-time All-Big Sky Conference All-Academics selection, a consensus All-American punter pick as a senior, and he finished his college career with 213 points, which ranks third in school history. As a kicker, he made 39 out of 65 field goal attempts, and 96 out of 100 PATs attempted.
Professional career
Detroit Lions
On April 11, 2008, Ernster was signed by the Detroit Lions. He was waived on July 29.