Abstract: An economizer in a solar tower plant and operating method of said plant the purpose whereof is to make use of the heat from the heat losses generated around the solar tower receivers (3) to preheat the fluid with which the saturated steam or superheated steam solar receivers are fed. When the heat from the losses absorbed by the economizer (2) is not sufficient to achieve the necessary minimum temperature, a secondary economizer (4) is used which takes live steam (prior to it entering the turbine) and increases the temperature of the feed water of the receiver (3).