Caches are known to consume a large part of total microprocessor energy. Traditionally, voltage scaling has been used to reduce both dynamic and leakage power in caches.However, aggressive voltage reduction causes process-variation-induced failures in cache SRAM arrays, thus compromising cache reliability. We present MultiCopy Cache (MC2), a new cache architecture that achieves significant reduction in energy consumption through aggressive voltage scaling whilemaintaining high error resilience (reliability) by exploiting multiple copies of each data item in the cache. Unlike many previous approaches,MC2 does not require any error map characterization and therefore is responsive to changing operating conditions (e.g., Vdd noise, temperature, and leakage) of the cache. MC2 also incurs significantly lower overheads compared to other ECC-based caches. Our experimental results on embedded benchmarks demonstrate that MC2 achieves up to 60% reduction in energy and energy-delay product (EDP) with only 3.5% reduction in IPC and no appreciable area overhead.