Techniques for conserving power by controlling program execution in a convergence device comprising a battery or other power source and at least one processor. The processor is configured to perform processing operations associated with voice call communication functions and to perform processing operations associated with data communication functions, and is operative to execute critical programs and noncritical programs. The convergence device stores, for at least a given one of a plurality of noncritical programs associated with the data communication functions, an identifier of at least one alternate capacity program capable of performing substantially the same function as the given program but having a different power source capacity associated therewith. Based at least in part on a power indicator representative of remaining capacity or another characteristic of the power source, execution of the given program may be replaced with execution of the alternate capacity program, such that an amount of power source capacity utilizable for the voice call communication functions is increased.