In the course of electricity production, not just during end use, significant amounts of energy and emissions could also be saved through more efficient technologies. For example, combined heat and power, or co-generation, systems produce both heat and electricity from a single fuel. These highly efficient systems conserve fuel by recovering and utilizing heat that is normally wasted in more conventional systems. Other technologies, such as gasification (turning fuel into a gas before burning it) and district energy systems (which provide thermal energy to multiple consumers), can be taken to increase the efficiency of fossil-fuel fired electricity generation.