Generator Transfer Switch Installation with your electrical project

What is generator transfer switch installation?

A transfer switch is the device that lets a generator power your house without any possibility of the two supplies being connected at once. It is not optional equipment: connecting a generator to a home's wiring requires a transfer switch or an equivalent listed device, and the reason is that generator current fed backwards onto the utility system can electrocute the line workers restoring your power. This page covers the electrical side - panel capacity, circuit selection and the permit.

How generator transfer switch installation actually works

1. 1

   Decide what you actually need running

   Most portable-generator installations back up selected circuits rather than the whole house: heating controls, the refrigerator, a well pump, some lighting, one or two receptacle circuits. Air conditioning, electric ranges, water heaters and dryers are usually out of reach on a portable generator.

   Watch forA circuit list assembled without checking the starting current of motor loads. A well pump can draw several times its running current at start-up, and a generator that copes on paper stalls in practice.

2. 2

   Manual, automatic, or an interlock kit

   A manual transfer switch means you start the generator and throw the switch yourself; an automatic one senses the outage and does it for you. A panel interlock kit is a third option - a listed mechanical device making it physically impossible to close the generator breaker and the main breaker at once. It is accepted in many jurisdictions, costs considerably less, and gives access to any circuit in the panel.

   Watch forInterlock kits that are not listed for your specific panel. A generic plate is not the same product, and an inspector will know the difference.

3. 3

   Inlet, cabling and where the generator stands

   A power inlet box is fitted outside and a cable of the right rating connects the generator to it. Position matters for a reason unrelated to electricity: generators produce carbon monoxide, and must be run well away from the house and never in a garage, a porch or anywhere partly enclosed.

   Watch forAn inlet fitted where the only convenient generator position is near a door, window or air intake. The carbon monoxide risk is what actually kills people.

4. 4

   Permit and inspection

   Permitted work in most jurisdictions. The inspection covers the switching arrangement, the inlet, and the grounding and bonding - which differ depending on the generator's own configuration.

What does generator transfer switch installation cost?

A manual transfer switch or interlock kit fitted alongside an existing panel is a half-day job plus parts. Automatic switches and whole-house arrangements cost substantially more, and are normally priced as part of a standby generator installation.

See the full generator transfer switch installation cost guide - by material, size and region →

If the number is the problem, here are the ways people pay for it →