Abstract: Wind energy efficiency（WEE）is used to estimate the net contribution of CO2 emission reduction from windgenerated electricity,which is an essential index to measure the efficiency of a power grid to accommodate wind energy.This paper takes into account that Chinas power grids mainly consist of coal-fired units,and it analyzes the cost components in accommodating wind power by means of unit commitment.This paper reveals how WEE changes with the operation modes and the parameters of coal-fired units,and the wind utilization proportion both in theory and by case study.The results show that the rules,approaches,prediction needs are quite unique in a coal power plant intensive grid.In addition,theory basics of windcoal coordinating operation is provided in this paper.