A method of operation of a conditioning system, such conditioning system, of the free cooling type for environments and particularly for computing centers, comprising: - a conditioning unit of the free cooling type provided with evaporative cooling means using water, - first fans for the exit to the outside environment of a stream of warm air, which is heated by the passage through said conditioning unit or in output from an environment to be air-conditioned, - second fans for introducing cool, conditioned air that originates from said conditioning unit, - means for accumulating reserve water which are interconnected to said conditioning unit, - means for detecting the presence of a flow of water in input to said accumulation means, which are interconnected with an electronic unit for the control and management of the conditioning system, - means for detecting the temperature at the point of delivery, to an environment to be air-conditioned, of said conditioning unit and comparing said detected temperature with a set setpoint temperature, said method being characterized in that it comprises the following operations: - based on the detected outside temperature, on the detected outside humidity, on the setpoint temperature for the air at the point of delivery into the environment to be air-conditioned, on the cost of electricity and on the cost of the water used by said conditioning unit, determining the optimum operating mode for said system from a plurality of operating modes, - if the optimum operating mode of the conditioning system does not require the consumption of water, then the cooling power is regulated by adjusting the speed of said first fans, said conditioning unit operating without the addition of water, - if the optimum mode requires the consumption of water, then detecting the presence of a flow of water in input to said accumulation means, - if the presence of a flow of water in input to said accumulation means is detected, then the operating mode is optimized with respect to the cost of the water and the cost of the electricity, - if the presence of a flow of water in input to said accumulation means is not detected, then check if the demand for cooling with respect to a set emergency setpoint temperature is met without water, - if it is found that the demand for cooling with respect to a set emergency setpoint temperature is not met without water, then the cooling power is regulated by adjusting the speed of said first fans, with the aid of the evaporative cooling means of the conditioning unit, i.e., with the addition of water, - if it is found that the demand for cooling with respect to a set emergency setpoint temperature is met without water, then the cooling power is regulated by adjusting the speed of said first fans with said conditioning unit operating without the addition of water. - a conditioning unit of the free cooling type provided with evaporative cooling means using water, - first fans for the exit to the outside environment of a stream of warm air, which is heated by the passage through said conditioning unit or in output from an environment to be air-conditioned, - second fans for introducing cool, conditioned air that originates from said conditioning unit, - means for accumulating reserve water which are interconnected to said conditioning unit, - means for detecting the presence of a flow of water in input to said accumulation means, which are interconnected with an electronic unit for the control and management of the conditioning system, - means for detecting the temperature at the point of delivery, to an environment to be air-conditioned, of said conditioning unit and comparing said detected temperature with a set setpoint temperature, - based on the detected outside temperature, on the detected outside humidity, on the setpoint temperature for the air at the point of delivery into the environment to be air-conditioned, on the cost of electricity and on the cost of the water used by said conditioning unit, determining the optimum operating mode for said system from a plurality of operating modes, - if the optimum operating mode of the conditioning system does not require the consumption of water, then the cooling power is regulated by adjusting the speed of said first fans, said conditioning unit operating without the addition of water, - if the optimum mode requires the consumption of water, then detecting the presence of a flow of water in input to said accumulation means, - if the presence of a flow of water in input to said accumulation means is detected, then the operating mode is optimized with respect to the cost of the water and the cost of the electricity, - if the presence of a flow of water in input to said accumulation means is not detected, then check if the demand for cooling with respect to a set emergency setpoint temperature is met without water, - if it is found that the demand for cooling with respect to a set emergency setpoint temperature is not met without water, then the cooling power is regulated by adjusting the speed of said first fans, with the aid of the evaporative cooling means of the conditioning unit, i.e., with the addition of water, - if it is found that the demand for cooling with respect to a set emergency setpoint temperature is met without water, then the cooling power is regulated by adjusting the speed of said first fans with said conditioning unit operating without the addition of water.