Methods of method of managing memory power usage in a computing device having two or more memory modules. By monitoring a system working set size of the computing device, a determination can be made if all active memory modules are needed for the system working set size. If not all active memory modules are needed for the system working set size, one or more of the active memory modules can be selected for power down. By evacuating data from the selected one or more memory modules, placing the evacuated one or more memory modules in a power-down state, and removing the powered-down memory modules from the active memory of the computing device, memory power usage can be reduced.