With the increased use of embedded/portable devices such as smart cellular phones, pagers, PDAs, hand-held computers, and CD players, improving energy efficiency is becoming a critical issue. To develop a truly energy-efficient system, energy constraints should be taken into account early in the design process; i.e., at the source level in software compilation and behavioral level in hardware compilation. Source-level optimizations are particularly important in data-dominated media applications that have become pervasive in energy-constrained mobile environments.This paper focuses on improving the effectiveness of energy savings from using multiple low-power operating modes provided in current memory modules. We propose a source-level data space transformation technique called array interleaving that colocates simultaneously used array elements in a small set of memory modules. We validate the effectiveness of this transformation using a set of array-dominated benchmarks and observe significant savings in memory energy.