He has previously played in Tippeligaen for Molde and Sandefjord. The young Norwegian striker was bought by Molde from Steinkjer in 2006. On 5 August 2010 he signed a two-year deal with Vejle.
In March 2012, Ertsås signed with Norwegian First Division side Alta after being released from his contract with Vejle.
He scored six goals in 20 matches for Alta during the 2012 season, when the team was relegated from the First Division. Ahead of the 2013 season, Ertsås signed a two-year contract with Hødd.