An evaluation algorithm is proposed to calculate the air-condtioning cooling load and the resulting power consumption in summer.A regression model between the cooling load and the daily maximum temperature in summer is built in accordance with actual temperature variation in summer of 2012,therefore the added cooling load stimulated by per degree of temperature increase is analyzed.An example of cooling load and power consumption in summer of China's main power grids is given to verify the feasibility of the proposed algorithm,which can provide reference for rational management and effective marketing of power grids.