Technologies are generally described herein for supporting program and data annotation for hardware customization and energy optimization. A code block to be annotated may be examined and a hardware customization may be determined to support a specified quality of service level for executing the code block with reduced energy expenditure Annotations may be determined as associated with the determined hardware customization. An annotation may be provided to indicate using the hardware customization while executing the code block. Examining the code block may include one or more of performing a symbolic analysis, performing an empirical observation of an execution of the code block, performing a statistical analysis, or any combination thereof. A data block to be annotated may also be examined. One or more additional annotations to be associated with the data block may be determined.