Automatic transfer switches keep your home safe during the transfer of power from your utility to the generator and back. Your transfer switch acts as a traffic controller by only allowing power to flow in one direction at a time. This prevents power surges that can severely damage your generator and your utility power, as well as your home itself. Using a transfer switch is the safest way to allow your generator to be fully automatic while protecting against damage. There are undoubtedly many different transfer switches to choose from. Some brands you might be familiar with are Asco, Generac (also can be mistakenly called a Generac Generator Transfer Switch), Kohler Transfer Switches, and Cummins Transfer Switches. Every company that produces transfer switches can assure you that they mechanically function equally. It is the specific type of switch you are looking at that will provide the differences.
Automatic Transfer Switches: There are two kinds of switches that are common; a transfer switch with a load center and a transfer switch without a load center. Without getting into anything too technical you are just making the decision to either power a couple of emergency circuits in the home or to power everything in your home. When you use a load center it can help you to keep the cost of the generator itself down because you are picking only a couple of necessary items to power in an emergency. When you have less to backup you won't need as many kWs. Since you are being selective there is very little chance of overloading the generator. Anything that is too much for your generator can simply be moved to a circuit that won't be backed up.
Whole House Transfer Switches: The next type is a whole house transfer switch. As the name implies, you are powering your entire house. You have to be a careful with this kind of switch and make sure that the generator can handle the entire load. If it can't then you may need to look into load-shedding (reducing) some of the items with a large demand. The last type of automatic switch isn't as common, a hybrid. It will basically combine the functions of a load center switch and a whole house switch. You probably want to consult with your electrician before purchasing an item like this. If it will work with your generator they are convenient and will save space. These kind of switches typically work best with new construction or homes with an abnormally large amount of circuits in the panel. If that is the case, you can use this single switch instead of having a transfer switch and a main panel. It can also be used in larger homes that may have multiple panels and you don't want to use every single circuit in those panels. Regardless of the situation always consult with either an experienced generator technician (we have several that you can speak with) or your electrician to see the advantages or disadvantages each switch will have for your specific installation.
Manual Transfer Switches: Manual transfer switches are exactly the same as the automatic transfer switches in basic functionality, however, they require you to transfer the generator power and utility power on your own. Since it is most commonly used in off-grid situations, where there is no utility, you don't have to worry about more than one power source coming on at the same time. That also means the unit wouldn't know how to come on or turn off automatically. If you are using the generator off-grid with solar power or a battery backup then your inverter will take the place of a transfer switch. If you choose to just turn the unit on and off then manually, make sure you shut off the main breaker on your service panel before turning on your generator so that you don't have both services on at the same time.