A laser efficiency of 4.2% at 4.2‐J output has been obtained from a self‐sustained discharge‐pumped XeCl laser using a novel high‐voltage prepulse technique to provide efficient energy transfer from a low‐impedance transmission line to the load. High‐pressure discharge‐pumped lasers now offer a reliable, efficient, and scalable alternative toebeams for many applications in the visible and ultraviolet regions of the spectrum.