Anomalous excess heat in Pd|D2O+H2SO4 electrolytic cells was confirmed using an accurate method of heat measurement, Seebeck Envelope Calorimetry. A cell was placed in the calorimeter, which measures the output heat flux directly and avoids many of the problems other methods have. The maximum excess power thus far was 1.3 W (or 11 W cm 3 ) with input power of 13 W at a current density of 0.4 A cm 2 . Calibrations were carried out before and after electrolysis experiments using a Pt|H2O+H2SO4 electrolytic cell, a dummy cell with inner resistor, or a pure resistor. Different calibrations gave consistent device constants within experimental error. Pd cathodes were analyzed by scanning electron microscopy and energy dispersive spectrometry. Unexpected elements were observed on the sample surface after electrolysis.