The energy loss induced by electron collisions in weakly ionized air plasma is calculated based on the electron energy distribution function that we obtained. Since there are a lot of low-energy-threshold molecular rotation and vibration excitations and the electron-molecule energy transfer is inefficient in elastic collision, the fraction of energy loss for electron elastic collision (less than 6%) is negligible. Among different collision processes the electron energy loss is dominant in different energy regions. As the effective electron temperature (or the reduced electric field) increases, the dominant energy loss process becomes sequentially rotational excitation, vibrational excitation, electronic excitation, collisional ionization, and accelerating ionized electrons. When E/N=1350 Td (or Te=14 eV), the average energy loss per ion-electron pair reaches a minimum value of 57 eV. By controlling the electric field according to the requirement in applications, we can control the electric field to achieve a higher energy efficiency.