PRICES MAY VARY. This is the most updated documentation for the Power System Analysis Toolbox (PSAT), a Matlab- and Octave-based software tool for electric power system analysis and control. The documentation describes the format and the models of all devices and controllers implemented in PSAT, as well as the routines (namely power flow, continuation power flow, optimal power flow, small signal stability analysis and time domain simulation), graphical interface, Simulink-based network design, and data formats supported by PSAT.