"E²" first aired on May 5, 2004. It received a 3.3/5% share, meaning that 3.3 percent of all households, and 5 percent of all households watching television at the time of the broadcast saw it. These were similar ratings to the previous episode, "The Forgotten", and slightly lower than the following episode, "". Compared to other shows in the same time slot, it placed sixth on the night, one place behind "Smallville" on The WB. In 2009, Den of Geek ranked E2 as the 7th best episode of Enterprise. In 2016, Hollywood Reporter placed it as 92nd best episode of all "Star Trek" up to that time.