The GenReady Load Center replaces the main circuit panel and has the ability to incorporate an automatic transfer switch (EZ Transfer Operator, Item# 165890) so all power switching is handled within one unit. It then becomes a hybrid panel capable of separating out only the electrical circuits the homeowner chooses to back up during a power outage. U.S.A. * 40 circuit capacity with the use of tandem breakers * Dimensions the same as a standard 42 circuit main load center * 42in.L x 15in.W x 4in.H * Uses standard Siemens load components * Works with Generac generators rated up to 125 Amps/30kW