A coin-shaped proton conductor made from metal oxides of strontium and cerium can be charged in a hot D2 gas atmosphere to produce excess heat. Anomalous heat evolution was observed from the proton conductors charged with alternating current at 5 to 45 V at temperatures ranging from 400 to 700°C. The anomalous heat produced temperature increases as much as 50°C. Excess heat was estimated as a few watts in most cases, totaling up to several kilojoules.