Home generators are designed to provide electricity in times of power outages or malfunctions for a short duration of time. Home stand-by generators not only light up the house in case of power outages but also, depending on their capacity, provide power to run appliances like air conditioners, refrigerators, furnaces, television and heaters.
If you plan on using a portable generator you must install a transfer switch. Transfer switches safely disconnect the generator feed from the main panel. The circuits that you would like to power up with your generator will be tied into the the transfer switch.
Both generator installation types, stand-by and portable generators with a transfer switch require a licensed electrical contractor.