When PERFORMANCE vs. INPUT POWER is plotted for any thermoelectric device, the resultant curve will appear as in the figure below; an inverted parabola. Performance can be DT (T_H - T_C), heat pumped at the cold side (Q_C), or as in most cases, a combination of these two parameters. Input power can be current (I), voltage (V) or the product of IV.

When we refer to the DTmax or Q_Cmax, we are referring to that point where the curve peaks. The same is true when referring to either Imax or Vmax. Since operating at or very near the peak is relatively inefficient, most devices are operated somewhere between 40% and 80% of Input Power MAX.

As stated, devices are normally operated on the near-linear, upward sloping portion of the curve. When automatic or closed loop temperature control is being used, current or voltage limits should be set below the MAX intercepts.