Energy confinement scalings for the thermal component of the plasma published thus far have a different dependence on plasma density and input power than do most scalings for the total plasma energy. With such thermal scalings, reactor performance (measured by the ignition margin MI , the ratio of the alpha power to the sum of the conducted and radiated losses) worsens with increasing density. The temperature dependence is significantly different as well and could lead to stable, ignited operation at temperatures lower than imagined with scalings based on the total plasma energy.