Surprisingly, the maximum PCE achieved with GaN-based LEDs, SLEDs, and LDs differs dramatically. Blue LEDs emit up to 83% of the electrical input power.⁶ Blue lasers reach about half that efficiency,⁴ but less than 10% PCE is reported for blue SLEDs.⁷ Many publications focus on the so-called efficiency droop, i.e., the relative efficiency reduction with rising current.⁸ The absolute energy efficiency is usually of greater importance, but it is often not revealed. This paper analyzes limitations of the peak PCE and explains the strong efficiency discrepancy between different emitter types. However, the direct comparison of measured efficiencies is difficult due to design and fabrication differences. We therefore employ advanced numerical simulations of identical emitter structures. Simulation results are validated by comparison to experiments.