An empirical scaling for the potential difference between the plug potential &Fgr;Pand the floating potential &Fgr;EPof an endplate is obtained in terms of end‐loss electron temperatures. Results from the GAMMA 10 tandem mirror [Phys. Rev. Lett.55, 939 (1985)] indicate that &Dgr;&Fgr;=&Fgr;P−&Fgr;EPscales much better with an effective temperatureTeff≡(1−&bgr;)TeL+&bgr;TeHthan with a single temperatureTeLorTeH, whereTeLandTeHare temperatures of the bulk and the high‐energy tail components of the end‐loss electrons and &bgr; denotes the flux fraction of theTeHcomponent. Moreover, the observed scaling is consistent with a recently developed theoretical model [K. Kuriharaetal., J. Phys. Soc. Jpn.61, 3153 (1992)].