Why home standby generator installations require an automatic transfer switch

A home standby generator is designed to work with an automatic transfer switch (ATS) so power can transfer safely between your utility service and the generator during an outage.

Environment

• Generac home standby generators (air-cooled and liquid-cooled) installed as a permanently wired backup power system.
• Residential electrical systems that require safe, code-compliant isolation between utility power and generator power.

Why an ATS is necessary

An ATS is a key part of a home standby system because it safely connects your home’s selected circuits to generator power. When utility power is restored, the ATS transfers the load back to the utility source.

For a deeper overview of what an ATS is and what it does, see What is an automatic transfer switch (ATS)? and How does an automatic transfer switch work?.

Important: ATS selection and installation should be performed by a qualified electrician and, when applicable, a Generac Independent Authorized Service Dealer (IASD). This article explains concepts and does not provide wiring instructions.

What could happen without an ATS

• The home may not isolate from the utility properly, which creates unsafe conditions and potential equipment damage.
• The generator may not receive the required control and sensing signals used for automatic operation in a home standby system.
• You may not get the intended “automatic” backup experience because the home standby system is designed to run with an ATS.

Note: Generac home standby generators are designed to be used with an ATS, not a manual transfer switch. For details, see Can I use a manual transfer switch with my home standby generator?.

Does my generator come with an ATS?

Some home standby generators are sold as part of a bundle that includes an ATS, while other packages require purchasing the generator and transfer switch separately.

Transfer switches are not always included because the correct ATS type and size can vary based on your home’s electrical service, how much of the home you want to back up, local code requirements, and load management needs. See If they are required, why doesn’t every home standby generator come with a transfer switch?.

Choosing the right ATS

ATS compatibility depends on your generator model and your electrical setup. To understand common compatibility considerations, see Automatic transfer switch compatibility guide.

If you are looking for general ATS education, including types, installation FAQs, and troubleshooting links, see Guide to automatic transfer switches, types, installation, and troubleshooting.

Get installation help

For help selecting or installing a home standby generator and ATS, work with a qualified electrician and a Generac IASD. Use the dealer locator to find an authorized dealer near you.

See also

• What is an automatic transfer switch (ATS)?
• How does an automatic transfer switch work?
• Automatic transfer switch compatibility guide
• If they are required, why doesn’t every home standby generator come with a transfer switch?
• Can I use a manual transfer switch with my home standby generator?