Hydraulic control systems are a known power dense form of actuation for large scale systems such as excavators, aircraft, and agricultural equipment. Fluid power at the meso-scale is much rarer since electromechanical actuation is usually sufficient for the application. However, the application at hand is a humanoid, lower extremity, bipedal robot, and with the required forces, electromechanical actuation would result in bulky actuators at the joints. Since not much has been done on this size, and scaling effects are not intuitive, it was not obvious what system pressures should be used to ensure the hydraulic control’s power density was taken advantage of. A study of the effects of operating pressure on system weight is presented herein. The results indicate there is indeed an optimal operating pressure in terms of overall weight.