Fast-paced life and the development of new technologies require a greater need for heat and electricity. In order to minimize the impact on the environment during production, the production of electricity and heat in the Sisak thermal power plant follows the latest modern technology, which meets the high environmental standards prescribed by the norms of the environmental permit. The Sisak thermal power plant is located on the right bank of the Sava River, from which the water needed for the operation of the plant is taken. The impact of the previous old blocks A and B for the production of electricity would not meet high environmental standards today. Modernized technology and the change of fuel from fuel oil to natural gas have largely led to more efficient work and an improved impact on the environment. The biggest positive change in the impact on the environment when the old blocks A and B stopped working in the new combo-cogeneration block C is visible through the reduced relase of emissions into the air. In accordance with the norms from the environmental permit, the parameters of wastewater are continuously measured before discharge into the Sava River. The measurement of noise protection is carried out at the outer limits of the thermal power plant, which belongs to the 5th zone of economic use. TE-TO Sisak is part of the HEP group, which has a high rate of both ecological and biological protection, which is implemented on an everincreasing scale in order to meet all prescribed standards.