Automatic transfer switch compatibility guide

This article is a guide to understanding automatic transfer switch (ATS) compatibility for Generac home standby generators and various electrical setups. It addresses common questions about matching ATS to home electrical systems, generator compatibility (both Generac and non-Generac), and even potential use with solar panel inverters, emphasizing the importance of reading the manual and contacting Generac with any questions.

Oct 8, 2025
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Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns.

Automatic transfer switch compatibility guide

Providing power transfer between the home's utility and generator, automatic transfer switches (ATS) are a crucial part of a home standby generator system. This article addresses common questions about automatic transfer switch compatibility with the home's electrical system, Generac generators, non-Generac generators, and other unique use cases.

Environment

This article applies to Generac automatic transfer switches and air-cooled home standby generators. To learn the basics of how an automatic transfer switch works, see here: How Does an Automatic Transfer Switch Work?

Automatic transfer switch (ATS) compatibility

See below for a list of common questions about ATS compatibility:

Does my ATS need to match my home's utility service?

In most applications, yes: The amperage of the ATS should match the amperage of your home's utility service. For example, if your home has 200-amp utility service, you will need a 200-amp automatic transfer switch.

An exception to this rule is for generators that provide partial home (or limited circuit) coverage.

An example of this is a home with 200-amp utility service, paired with a 100-amp automatic transfer switch that works with a 14kW generator to provide power only to select circuits in the home (such as a sump pump, heater, and refrigerator).

Bottom line: The ATS amperage must be equal to or less than the amperage of the home's utility service.

Do I need a service entrance rated ATS, or a non-service entrance rated ATS?

It depends on your home's existing electrical system, and the desired configuration of your ATS. See here for more information on the difference between a service entrance rated and non-service entrance rates ATS: What's the Difference Between A Service-Entrance Rated and Non Service-Entrance Rated Transfer Switch?

To determine the correct ATS for your needs, contact a Generac authorized dealer.

I have two separate electrical panels. Can I connect them both to one transfer switch?

It depends on your location, and the requirements of your utility company. A Generac authorized dealer can advise on the installation requirements for ATS installations where multiple electrical panels are present.

In most cases, if multiple electrical panels are present in a home, they will each need a separate, dedicated transfer switch.

For example, if two separate 200-amp electrical panels are present in a home, they may each need their own dedicated 200-amp transfer switch. Again, this depends on the requirements of your utility company.

What size transfer switch do I need for my Generac generator?

The home's utility service is the primary factor in determining the size of an ATS. There should never be a case where a generator's main line circuit breaker exceeds the capability of the ATS.

Is my Generac ATS compatible with a non-Generac home standby generator?

In many cases, the method and origin of power transfer is fundamentally different between Generac and non-Generac products.

In Generac products, the 'brain' that decides when and how power transfer should occur exists in the Generator's control panel. With other manufacturers, the 'brain' may exist in the ATS instead. This creates a 'two-brain' conflict that may render a Generac ATS incompatible with a non-Generac generator. This mismatch in power transfer execution is why we recommend pairing a Generac ATS with a Generac generator. Typically, they are not compatible.

To determine if your Generac ATS is compatible with a non-Generac generator, we recommend consult the generator manufacturer.

Is my Generac generator compatible with a non-Generac ATS?

In some circumstances, a non-Generac ATS with a two-wire control system may be compatible with Generac generators. We offer a two-wire start kits to accommodate specific installation scenarios that require it: What is Two-Wire Start for Home Standby Generators?

To determine compatibility with your non-Generac ATS with our two-wire start kit, consult with the ATS manufacturer.

Can my Generac home standby ATS be used to transfer power for my solar panel inverter?

No. This is not a recommended application.

I need to replace my Generac generator, but my ATS is still in good condition. Are they compatible?

In this scenario, two basic requirements should be met:

Both the generator and the transfer switch are non-industrial.
They have the same voltage ratings and phases (example: both are 120/240V, 1 phase)

Additional considerations:

We recommend checking with your local Generac authorized service dealer to confirm that your current ATS meets the requirements of local or national electrical codes that may have been updated since the ATS was initially installed.
If your Generac ATS was manufactured prior to 2010, it likely does not include the T1 circuit and fuse (which charges the generator's battery). This will require a retrofit kit.
The part number for the T1 retrofit kit is 0G92540SRV. It can be purchased on Ordertree or through a local Generac service dealer
Note: Generac does NOT recommend untrained end users attempt to service fuses in transfer switches. To find a local authorized service dealer, see here.