In the present work, the current-voltage characteristic at 700 degreesC across a thin film of Ce0.8Gd0.2O1.9 (CGO) was analyzed by local equilibrium theory. The performance of a Ni-Ce0.8Sm0.2O1.9 (CSO20) anode and a La0.6Sr0.4Co0.8Fe0.2O3-Ce0.8Gd0.2O1.9-Ag (LSCF-CGO-Ag) cathode was studied at 500-700 degreesC by three-probe complex impedance measurements. If the electrodes are used on a thin film of Ce0.8Gd0.2O1.9 (CGO20) electrolyte, the calculation showed that the maximum energy conversion efficiency at 700 degreesC could reach 0.43, where the power density was 0.62 W/cm(2), which is large enough for practical operation.