Large homes have large electrical systems, so they may have special requirements when a residential standby generator is installed. These requirements could extend past the power rating of the unit.
Even the service panels that accommodate the higher current ratings only have room for so many circuit breakers. A large home with many circuits and many appliances that are permanently wired may require two or more service panels, each with specific circuit breakers assigned to them so power can be properly distributed through the house.
To do this, the generator has to be rated to supply all of the devices that it powers. If an Automatic Transfer Switch (ATS) is installed between the main service panel and the meter, it becomes part of the service equipment.
Today, many modern homes have electric requirements that exceed the requirements from 20 and 30 years ago. The minimum service for a single-family home that is built today is 100 amps. Some municipalities require new electrical systems to be a minimum of 1125 or 150 amps.
When looking at large homes, it isn’t unusual to see them with more than one furnace, a five-ton air conditioning unit, a hot tub, a swimming pool with heaters, and many other items. The loads can quickly add up to 400 amps.
A service panel that is rated at 200 amperes can take on 40 single-pole circuit breakers. If more circuits are needed, another service panel or two may be needed. When the required service is 200 amperes, it is common to have the installation split between two panels. If the required service is 300 amps, then two 150 amp panels will be needed. If the required service is 400 amps, then two 200 amp panels will be used.
If the installation is especially large, then the installation may have additional panels and sub panels.