Maximum power point ($P_{\max }=V_{\mathrm{mp}}{I}_{\mathrm{mp}}$)

The maximum power point is the operating voltage $V_{\mathrm{mp}}$ and output electric current $I_{\mathrm{mp}}$ at which a source delivers its largest electrical power, $P_{\max }=V_{\mathrm{mp}}{I}_{\mathrm{mp}}$. It is found along the device's current–voltage curve under specified illumination and temperature.

For a smooth solar-cell output curve written with delivered current positive, an interior maximum satisfies $d(VI)/dV=I+VdI/dV=0$. The short-circuit current and open-circuit voltage are useful endpoints but neither delivers power, because one factor is zero at each endpoint. Changing illumination or temperature moves the maximum power point, motivating maximum power point tracking in the connected power converter.