The article presents the results of experimental studies on the operational efficiency of a steam boiler house. The installation of a steam boiler house consists of a set of shell boilers and a technological installation. The article discusses the issues related to the thermal operational efficiency of a steam boiler house with steam shell boilers fired by gaseous and liquid fuels. The results of tests of the operational efficiency of a steam boiler in its operating conditions are presented. The research was carried out for 18 months in the steam boiler room of the Provincial Hospital. Test results obtained at the real object were compared to research results according to PN-EN 12953-11. The tests proved that the actual thermal operational efficiency is lower than that determined by the standard. This is due to the fact that under real conditions the amount of components responsible for its loss is larger than the norm for its calculation.