Captain Universe's powers and power levels vary from partner to partner, presumably to meet the demands of the job at hand. The Uni-Power also enhances the powers and abilities of a host who already has such powers and abilities. Powers that remain relatively constant include:
a sort of cosmic consciousness. Captain Universe can sense things on a subatomic level or at great distances. This power can also force someone to tell the truth.
Captain Universe can divert an energy flow in a different direction or convert it into a different type of energy. Diverting the flow of gravitons, for example, allows flight. Captain Universe can also change matter at the atomic level, for instance, to transmute one substance into another or to change an object's shape.
(or the Uni-Power itself) protects against extremes in temperature.