This article substantiates the need for widespread use of non-conventional energy resources for heat supply. Designs of lowpower boilers that can burn natural gas, biogas and wood are presented. The analysis of information on the determination of the dew point temperature of resins during wood combustion has been carried out. A mathematical model has been developed for a low-power hot-water boiler, which allows one to take into account the intensification of heat transfer in the fire-tube bundle, the mode of condensation of resins and water vapor. Numerical studies have been carried out and the main indicators of the boiler operation on different fuels have been determined.