The electrical power system (EPS) is an essential part of a satellite. It distributes, stores and generates the electric power for autonomous operation of the satellite in space. Through standardizations in the CubeSat community a common structure of EPS is established. The thesis explains both the functioning and the requirements of electrical power systems. Furthermore, two EPS are presented that are currently commercially available and have been used in other CubeSats. The Naval Postgraduate School (NPS) is currently developing a 1U Cubesat (NPS-SCAT) and the EPS board used has...