Basic characteristics of energetic sources. Secondary energetic source - understanding of deffinition. Energy losses. Potential of energy sources. Fuel conservation. Secondary energetic fuels. Secondary energetic heat. Waist/exhaust heat boilers. Gas/fuel gas turbines. Microturbines. Low-potential energy. Heat pumps. Utilization of cold water enthalpy. Pressure as a secondary energetic source. Secondary energetic sources of other industrial branches. Ecological and economical point of wiev of secondary energetic sources.