Most commercial electricians work with standard voltages of 120V, 208V, 240V, 277V, and 480V in commercial buildings. These voltages are commonly used for lighting, outlets, appliances, and various electrical systems. The specific voltage depends on the building's electrical design and the equipment being installed. Electricians must follow local electrical codes and safety regulations when working with different voltage levels to ensure proper installation and safe operation of electrical systems in commercial settings.