Editing Electrolysis (section)

===Energy changes during electrolysis===
The amount of electrical energy that must be added equals the change in [[Gibbs free energy]] of the reaction plus the losses in the system. The losses can (in theory) be arbitrarily close to zero, so the maximum [[thermodynamics|thermodynamic]] efficiency equals the [[enthalpy]] change divided by the free energy change of the reaction. In most cases, the electric input is larger than the enthalpy change of the reaction, so some energy is released in the form of heat. In some cases, for instance, in the electrolysis of [[steam]] into hydrogen and oxygen at high temperature, the opposite is true and heat energy is absorbed. This heat is absorbed from the surroundings, and the [[heating value]] of the produced hydrogen is higher than the electric input.