This paper briefly describes the reasons for determining the thermal efficiency of power plant boilers by anti-equilibrium method.

Answer: (1) The positive balance method requires the boiler load to be strictly constant during the experiment, and it is difficult to realize the boiler load to be strictly constant during the experiment in engineering practice.

(2) The positive balance method requires accurate determination of fuel consumption. It is difficult to accurately determine the fuel consumption of large boilers (the evaporation capacity of power plant boilers is generally above 670t/h).

(3) The anti-balance method can know the composition of each loss in detail and determine the boiler efficiency, and does not require the boiler load to be strictly constant.