An electrical power supply system includes a freestanding primary electrical unit, a non-freestanding accessory unit, and an accessory unit support system. The primary electrical unit includes a freestanding cabinet containing a primary electrical component. The accessory unit includes a non-freestanding accessory cabinet containing an accessory electrical component. The accessory unit support system is configured to couple the accessory cabinet to the primary cabinet such that the accessory unit is thereby structurally supported by the primary electrical unit. The accessory cabinet can be selectively decoupled from the primary cabinet and alternatively structurally supported using the accessory support system.