Radioisotope cells (RCs) and a direct sodium borohydride/hydrogen peroxide fuel cell (NaBH4/H2O2 FC) are compared to conventional chemical batteries through Ragone plots of theoretical (RCs) and experimental (chemical batteries and FC) data. It is found that the RCs are projected to have superior specific energy but inferior specific power, while the borohydride/peroxide FC shows an impressive range for both parameters. Thus, RCs may be especially useful in battery charging, communications, or other applications that require a long-lived, low-power source or periodic pulses of energy. While the borohydride/peroxide FC can be scaled to a variety of high-power applications, it is especially well suited for space and undersea use where air independence is essential.