Methods and apparatus are provided for choosing an energy-efficient coolant temperature for electronics by considering the temperature dependence of the electronics' power dissipation. This dependence is explicitly considered in selecting the coolant temperature T0 that is sent to the equipment. To minimize power consumption PTotal for the entire system, where PTotal=P0+PCool is the sum of the electronic equipment's power consumption P0 plus the cooling equipment's power consumption PCool, PTotal is obtained experimentally, by measuring P0 and PCool, as a function of three parameters: coolant temperature T0; weather-related temperature T3 that affects the performance of free-cooling equipment; and computational state C of the electronic equipment, which affects the temperature dependence of its power consumption. This experiment provides, for each possible combination of T3 and C, the value T*0 of T0 that minimizes PTotal. During operation, for any combination of T3 and C that occurs, the corresponding optimal coolant temperature T*0 is selected, and the cooling equipment is commanded to produce it.