A method of implementing a redundant cooling system for providing a predetermined maximum cooling load for air in a conditioned space, the method comprising: providing a plurality of variable refrigerant flow air cooling units (101, 102, 103) comprising a variable speed compressor, wherein the number of air cooling units (101, 102, 103) is at least one more than required to meet the predetermined maximum cooling load when operating the air cooling units (101, 102, 103) at up to a maximum cooling capacity; coupling the plurality of variable refrigerant flow air cooling units (101, 102, 103) in thermal communication with the air in the conditioned space; and determining a select optimum operating condition for each of the plurality of variable refrigerant flow air cooling units (101, 102, 103) which will result in a lowest overall energy consumption for the redundant cooling system, while maintaining an average temperature of the air in the conditioned space at a required setpoint; and a) operating the variable speed compressors of each of the plurality of refrigerant flow air cooling units (101, 102, 103) at approximately the same speed when the cooling output of each cooling unit (101, 102, 103) is above that at which a maximum energy efficiency ratio of the unit occurs; and b) at least one of i) turning off the variable speed compressors of one or more of the plurality of air cooling units (101, 102, 103) when the average required cooling output of all of the plurality of air cooling units (101, 102, 103) is below that at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs; and ii) operating each of the plurality of air cooling units (101, 102, 103) at about the point at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs. providing a plurality of variable refrigerant flow air cooling units (101, 102, 103) comprising a variable speed compressor, wherein the number of air cooling units (101, 102, 103) is at least one more than required to meet the predetermined maximum cooling load when operating the air cooling units (101, 102, 103) at up to a maximum cooling capacity; coupling the plurality of variable refrigerant flow air cooling units (101, 102, 103) in thermal communication with the air in the conditioned space; and determining a select optimum operating condition for each of the plurality of variable refrigerant flow air cooling units (101, 102, 103) which will result in a lowest overall energy consumption for the redundant cooling system, while maintaining an average temperature of the air in the conditioned space at a required setpoint; and a) operating the variable speed compressors of each of the plurality of refrigerant flow air cooling units (101, 102, 103) at approximately the same speed when the cooling output of each cooling unit (101, 102, 103) is above that at which a maximum energy efficiency ratio of the unit occurs; and b) at least one of i) turning off the variable speed compressors of one or more of the plurality of air cooling units (101, 102, 103) when the average required cooling output of all of the plurality of air cooling units (101, 102, 103) is below that at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs; and ii) operating each of the plurality of air cooling units (101, 102, 103) at about the point at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs. a) operating the variable speed compressors of each of the plurality of refrigerant flow air cooling units (101, 102, 103) at approximately the same speed when the cooling output of each cooling unit (101, 102, 103) is above that at which a maximum energy efficiency ratio of the unit occurs; and b) at least one of i) turning off the variable speed compressors of one or more of the plurality of air cooling units (101, 102, 103) when the average required cooling output of all of the plurality of air cooling units (101, 102, 103) is below that at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs; and ii) operating each of the plurality of air cooling units (101, 102, 103) at about the point at which the maximum energy efficiency ratio of the air cooling unit (101, 102, 103) occurs.