Abstract: In a capacitor-based energy storage system, in which the capacitor charging voltage is on the same order of magnitude as the system output voltage, the time between recharges for a given energy release rate is extended by producing an intermediate regulated capacitor output of a voltage having a lower order of magnitude and then stepping that voltage back up to the system output voltage through the use of an inverter. Regulation of the capacitor output voltage may be achieved through the use of a capacitor-voltage-dependent variable-duty-cycle switching transistor and an averaging network, which together maintain a level inverter input voltage independently of the capacitor voltage. The cycle control is powered by a rechargeable battery which recharges from the inverter input but cannot drive the inverter, and current and temperature sensing means are provided to control the transistor so as to limit the current draw through the transistor and to prevent battery overheating during operation.