1. A server rack, comprising:vertically stacked first and second shelves, wherein the first shelf is located above the second shelf;
a vertical bus secured to the back side of the server rack, located substantially at the center of the server rack, and configured to distribute power to a plurality of sets of power supply units, each set of power supply units located next to and associated with a corresponding shelf in the server rack;
a first horizontal bus conductively coupled to the vertical bus at approximately its center and conductively coupled to a first set of power supply units; and
a second horizontal bus conductively coupled to the vertical bus at approximately its center and conductively coupled to a server located on the first shelf and equidistant from first and second sides of the server rack;
wherein the first set of power supply units comprises at least two power supply units that are separated and located on left and right sides of the server and each distribute power to the server through the vertical bus and the first and second horizontal buses.