The corrected 3D Ewald method is used to verify charged sheets method results that show increasing double-layer capacitance with increasing temperature in the low effective temperature region. The restricted primitive model is used where ions are represented as charged hard spheres and the solvent is represented by a uniform dielectric constant. It is shown that the capacitance temperature plot for the test system exhibits increasing capacitance with increasing temperature in the low effective temperature region, which contradicts common theories of the electrochemical interface. For this system, the corrected 3D Ewald method results coincide well with the charged sheets method results.