ELECTRICITY STORAGE SYSTEM

An electricity storage system 100 has secondary battery housing system racks 10a to 10e in which secondary batteries 140 and circuit blocks 40 are respectively housed, and a power converter housing rack 18 in which a power converter 20 is housed, and which is orderly disposed together with the plurality of secondary battery housing system racks. The secondary battery housing system rack having a positive-electrode-side terminal 41 directly connected to a positive-electrode-side terminal 21 of the power converter 20 by a positive-electrode bus 1 and the secondary battery housing system rack having a negative-electrode-side terminal 42 directly connected to a negative-electrode-side terminal 22 of the power converter 20 by a negative-electrode bus 2, are different from each other.