Summary form only given. Capacitors that must operate with a high repetition rate and high energy generate heat, which detracts from electrical performance. The traditional technique of using air on the exterior of a capacitor is modest compared to liquid cooling applied to the interior of a capacitor. A form of high-pressure microchannel cooling applied to one electrode in a capacitor can achieve a high convective cooling rate over a substantial electrode area. This liquid cooling can transport substantial amounts of heat from an internal dielectric out of a capacitor. Interfacing the hydraulic system to the electrical circuit can be simplified by using a low potential or grounded electrode. Microchannel cooling that can dissipate approximately 3 kW/cm/sup 2/ will be discussed along with electrical performance and a thermal circuit for internal heat dissipation within a capacitor.