Model calculations of the interaction of energetic protons with the thermosphere are performed to evaluate the heating efficiency. All energy channels which are responsible for the neutral gas heating are taken into account. The heating efficiency is evaluated for the Maxwellian and power law spectra of precipitating protons. It is shown that the altitude profile of heating efficiency is dependent on the proton spectrum. For a Maxwellian distribution. The maximum value of heating efficiency is found to be 0.68 for the PCA event of March 21, 1969, which is considered in the model calculations for power law spectrum. ¿ American Geophysical Union 1988