Heat transfer rates to spray droplets under conditions of a loss-of-coolant accident in a light water reactor have been calculated by two different droplet models: the rigid droplet model and the complete mixing droplet model For calculating the heat transfer rates, a computer program, CONDENSE, was developed. The program was designed to calculate the respective model with the corresponding input data. The difference between the two models in spray heat transfer efficiency and the effects of droplet size, initial velocity, spray angle, and gas temperature on the efficiency were revealed by calculations. In addition, the dependence of the efficiency on the fall distance of a droplet, which had not been reported despite its importance in evaluating the spray effectiveness in a vessel, was revealed.