According to a novel atomic model, the predominant source of heat of the phenomenon called cold fusion is the electrocatalytically induced reaction whereby hydrogen atoms undergo transitions to quantized energy levels of lower energy than the conventional ground state. These lower energy states correspond to fractional quantum numbers. The hydrogen electronic transition requires the presence of an energy hole of ∼27.21 eV provided by electrocatalytic reactants (such as Pd2+/Li+, Ti2+, or K+/K+) and results in “shrunken atoms” analogous to muonic atoms. In the case of deuterium, fusion reactions of shrunken atoms predominantly yielding tritium are possible. Calorimetry of pulsed current and continuous electrolysis of aqueous potassium carbonate (K+/K+ electrocatalytic couple) at a nickel cathode is performed in single-cell dewar calorimetry cells. Excess power out exceeded input power by a factor of >37.