A method includes monitoring power usage for a storage system that includes a set storage units at a first level of storage granularity and a set of storage sub-units at a second level of storage granularity, wherein the second level of storage granularity is finer than the first level of storage granularity. The method further includes assigning a non-uniform power budget to the set of storage units and adjusting a power budget for the storage sub-units according to the non-uniform power budget assigned to the storage units. A corresponding computer program product and computer system are also disclosed herein.