The processes which tend to increase the equilibrium kinetic temperature of interstellar matter are considered in detail. The equations for the energy gained by photoelectric ionization of H and other atoms, by the photodetachment of electrons from H, and by photoelectric emission from solid grains are put into a form suitable for numerical computation. Since the electrical charge on the grains enters into the problem, the various physical processes, such as the sticking probability of electrons, which determine the magnitude of the charge on a grain, are also discussed, and the quantitative physical in- formation available on these processes is summarized. The kinetic energy transferred from cosmic rays to the much-less-energetic atoms and grains is treated briefly. The processes which tend to decrease the equilibrium kinetic temperature and the ftnal equilibrium temperatures to be expected will be dis- cussed in a subsequent paper