In one embodiment, a mobile electronic device has a host controller, an energy-saving encoder, an energy-saving decoder, and a multi-level cell (MLC) NAND flash memory. The host controller provides raw user data to the energy-saving encoder in k-bit segments. The energy-saving encoder encodes each k-bit segment into an n-bit segment of encoded user data for programming the MLC NAND flash memory as a p-symbol codeword, where (i) k is smaller than n (ii) p(=n/log2 m) MLCs are used to store the p-symbol codeword (iii) each MLC stores one symbol of the codeword. The energy-saving decoder is adapted to read p-symbol codewords from the MLC NAND flash memory and decode each p-symbol codeword into a k-bit segment of raw user data for provision to the host controller. The host controller is adapted to vary k and n to conserve usage of power or memory-space, as needed.