Consider an energy-harvesting receiver that uses the same received signal both for decoding information and for harvesting energy to power its circuitry. When the receiver has limited battery size, a signal with bursty energy content may cause power outage since the battery will drain during intervals with low signal energy. The energy content in the signal may be regularized by requiring that sufficient energy is carried in every subblock duration. In this paper, we study constant subblock-composition codes (CSCCs) where all subblocks in every codeword have the same composition, and this composition is chosen such that the real-time energy requirement at the receiver is met. For a given energy storage capacity at the receiver, we give a necessary and sufficient condition on the subblock length for avoiding outage. We show that CSCC capacity on a discrete memoryless channel can be efficiently computed by exploiting certain symmetry conditions, and compare it with the capacity of constant composition codes. We provide numerical examples highlighting the tradeoff between delivery of sufficient energy to the receiver and achieving high information transfer rates.