A system and method for efficiently powering down banks in a cache memory for reducing power consumption. A computing system includes a cache array and a corresponding cache controller. The cache array includes multiple banks, each comprising multiple cache sets. In response to a request to power down a first bank of the multiple banks in the cache array, the cache controller selects a cache line of a given type in the first bank and determines whether a respective locality of reference for the selected cache line exceeds a threshold. If the threshold is exceeded, then the selected cache line is migrated to a second bank in the cache array. If the threshold is not exceeded, then the selected cache line is written back to lower-level memory.