pA heat pump system can produce an amount of heat energy that is greater than the amount of energy used to run the heat pump system. Thus, a heat pump system is considered to be a machine system that can use energies efficiently, as is the load leveling air-conditioning system utilizing unutilized energies at high levels. Adaptations of gas turbines for industrial, utility, and marine-propulsion applications have long been accepted as means for generating power with high efficiency and ease of maintenance. Cogeneration with gas turbine is frequently defined as the sequential production of useful thermal energy and shaft power from a single energy source. For applications that generate electricity, the power can either be used internally or supplied to the utility grid. This Special Issue intends to provide an overviews of the existing knowledge related with various aspects of Small-Scale Energy Systems with Gas Turbines and Heat Pumps, and contributions on, but not limited to the follo