A generator is wired into a house's breaker box with a transfer switch. These switches are installed next to the breaker box and allow for the breaker box to safely switch from utility power to generator power. Due to the many laws, electrical codes and safety issues involved, installation is best done by a qualified electrician familiar with residential wiring.
A transfer switch is required by the National Electric Code for any power connection to the house. Transfer switches isolate the selected circuits of a house from the utility lines, which prevents back-feed that could damage the generator, start a fire or even electrocute the technician working on the power lines.
The transfer switches can be either manual or automatic. Manual models are less expensive and can include up to 16 separate circuits that are assigned to a different household load and can be turned on and off to manage the generator's power usage and effectiveness. They also need to be manually turned on when there is a power outage and turned off when power is restored.
Automatic transfer switches can be programmed based on user-determined priorities and generator power flow. They are capable of automatically switching between generator power and utility power.