The work is devoted to research on the improvement of thermal energy production technologies in gas-burning heating boiler plants while improving their environmental performance. The thermal-moisture modes of operation of boiler plants with waste gas recirculation systems into combustion air were studied. According to the research results, it is shown that the introduction of recirculation gases leads to a decrease of 150 ÷ 250 °С in the adiabatic combustion temperature due to the need to spend fuel heat to heat the introduced ballast. The use of recirculation leads to a decrease in boiler efficiency by 1.3 ÷ 3.1%, depending on its load and the proportion of waste gases recirculation from 10 to 20%; the use of waste gas heat-recovery systems with heating of return heat-network water and combustion air provides a resulting increase in efficiency with a heat-recovery system and recirculation, which is 1.0 ÷ 3.8%.