A review on boilers energy use, energy savings, and emissions ...
Energy can be lost due to open condensate tank [22], [36]. Boilers energy efficiency varies from 20% to 92% depending on the fuel type and purpose of the boiler [24]. Thermal efficiency of coal fired boilers varies between 81% and 85%, for oil between 78% and 81% and for gas between 76% and 81% (HHV).