Automatic transfer switch that can be installed in the Siemens series of Genready load centers. The switch installs inside the load center and provides an automatic means of switching between utility and generator power. When connected to a Siemens or compatible standby generator, operation is completely automatic. When used in conjunction with a Siemens Genready load center, one enclosure replaces what has typically required 3 (load center, transfer switch, and sub panel).