Merits

        1. Plant people can evaluate quickly the efficiency of boilers

        2. Requires few parameters for computation

        3. Needs few instruments for monitoring

Demerits

        1. Does not give clues to the operator as to why efficiency of system is lower

        2. Does not calculate various losses accountable for various efficiency levels

        3. Evaporation ratio and efficiency may mislead, if the steam is highly wet due to water carryover