Combined production of electricity and heat in the same plant generally takes the name of cogeneration. Combined production can increase the efficiency of using fossil fuel up to 80%; which corresponds to lower costs for the supply of fossil fuel and lower emissions of pollutants and greenhouse gases (so-called climbering gases) with respect to the separate production of electricity and heat. Generally, thermal power plants have low energy efficiency: only 40-50% (up to 55% in most modern installations) of thermal energy contained in fossil fuels is transformed into electricity. the remaining amount is dissipated into the environment without any use. In some cases, however, such residual heat energy can be used in industry, for example in the form of steam, or it can be used for civil uses, such as heating buildings. Combined production plants therefore convert primary energy, any source, into electricity and thermal energy (heat), produced together and both considered useful effects.