Yes, during the two-day installation process someone must be home to provide the technicians access to your house for wiring and gas piping the generator.
During the first day, you can expect the power to be turned off for a period of 2-4 hours depending on the complicity of the installation.
On the second day, we will need to turn off the gas for a period of 1 hour. Once gas is restored, our plumbing tech will need to gain access to the common areas of your home to ensure that all of the pilot lights are re-lit on all of your gas fired appliances. Please note some appliances may not have a pilot light or automatically light themselves once gas is restored.