To utilize solar energy at a high temperature, a parabolic dish/cavity receiver configuration is often used. The energy loss mechanisms of such a system are analyzed. System efficiency is defined as the power absorbed by the working fluid circulating in the cavity divided by the solar power falling on the concentrator aperture. Power profiles produced in cavities of varying geometry with concentrators of varying rim angle are also discussed. It is found that varying concentrator rim angle and cavity geometry can greatly affect the cavity power profile without a large effect on system efficiency. Cavity isothermality often requires a nonlinear power profile , particularly in a thermochemical system. The methodology described can be used to optimize concentrator/cavity design variables.