Installation

Generator and transfer switch installation

A generator must connect through a transfer switch or an approved interlock so it can never feed power back into utility lines. Electricians install standby generators, portable generator inlets with interlocks, and the transfer equipment for both.

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A standby generator on a concrete pad beside a house

About generator installation

Backfeeding a house through a dryer outlet with a 'suicide cord' can electrocute line workers and burn out a generator when power returns. A properly installed inlet box and interlock or transfer switch is the safe way to run a portable generator.

Standby generators start automatically. They need a concrete or composite pad, a gas line from a licensed plumber or gas fitter, an automatic transfer switch and a permit.

Generator Installation at a glance: Installation
Who does the work: An independent licensed electrician
Urgent calls: Usually scheduled
Typical first step: Size the load

Signs you need this

Frequent outages from storms, ice or heat
Medical equipment, sump pumps or freezers that cannot lose power
A portable generator with no safe way to connect
Planning a whole-home standby unit

What the electrician does

1
Size the load
Circuits that must stay powered are listed and the generator sized.
2
Choose the connection
Inlet and interlock, manual transfer switch or automatic transfer switch.
3
Install and inspect
Permitted installation, gas connection by a licensed fitter where needed, and inspection.

What affects the cost

Electricians set their own prices. These are the factors that move a quote up or down, so you can compare like for like.

Portable inlet versus standby system
Generator size
Transfer switch type
Distance from panel and gas source
Pad, permits and inspection

What you can do safely, and when to stop

Safe to do

✓ Run portable generators outside, at least 20 feet from doors and windows

Stop and call

✕ Never backfeed through an outlet
✕ Never run a generator in a garage

Key terms

Automatic transfer switch (ATS): A switch that detects an outage, starts the generator and moves the home's load to it.
Backfeeding: Sending generator power back through the home's wiring to the utility lines; dangerous and illegal.
Power inlet box: An exterior connection where a portable generator's cord plugs in safely.

Generator Installation FAQ

Is an interlock kit legal?

Listed interlock kits are accepted in many jurisdictions when installed with a permit. Your electrician will know the local rule.

What is the difference between a portable and a standby generator?

A portable generator is wheeled out and connected when needed. A standby generator is permanently installed, runs on natural gas or propane, and starts automatically through a transfer switch.

Can I plug a generator into a wall outlet?

No. Backfeeding through an outlet can energize utility lines and injure line workers, and it can damage equipment. Use a transfer switch or an interlock with an inlet.

What is an interlock kit?

A mechanical device on the main panel that makes it impossible to turn on the generator breaker while the main breaker is on, allowing a portable generator to safely power chosen circuits.

What size generator do I need?

It depends on what you want to run: a few essentials such as a furnace, refrigerator and lights, or the whole house. An electrician sizes it from the loads and the starting current of motors such as air conditioners.

Where can a generator be placed?

Outdoors, at clearances from windows, doors and vents set by the manufacturer and local code, because exhaust contains carbon monoxide. Never run a generator in a garage or basement.

Does a standby generator need a permit?

Yes, usually electrical and often gas permits, plus any HOA approvals. The electrician and the gas installer coordinate inspections.

How long does a standby generator installation take?

The installation itself is often a day or two once the pad, gas line and permits are ready; ordering and permits can take longer.

Where electricians offer this

Local guides to generator installation, with permit offices, housing and utility notes for each city:

Available through our network in 47 states and DC. Metro guides:

Birmingham, AL Huntsville, AL Phoenix, AZ Tucson, AZ Little Rock, AR Los Angeles, CA San Diego, CA Sacramento, CA San Francisco, CA San Jose, CA Fresno, CA Bakersfield, CA Long Beach, CA Oakland, CA Pasadena, CA Denver, CO Colorado Springs, CO Hartford, CT New Haven, CT Wilmington, DE Washington, DC Miami, FL Tampa, FL Orlando, FL Jacksonville, FL Saint Petersburg, FL Fort Lauderdale, FL Atlanta, GA Boise, ID Chicago, IL Indianapolis, IN Des Moines, IA Wichita, KS Louisville, KY New Orleans, LA Baton Rouge, LA Shreveport, LA Baltimore, MD Boston, MA Grand Rapids, MI Minneapolis, MN Saint Paul, MN Kansas City, MO Omaha, NE Lincoln, NE Las Vegas, NV Reno, NV Manchester, NH Trenton, NJ Newark, NJ Albuquerque, NM New York, NY Albany, NY Syracuse, NY Charlotte, NC Greensboro, NC Columbus, OH Cleveland, OH Dayton, OH Akron, OH Oklahoma City, OK Tulsa, OK Portland, OR Philadelphia, PA Pittsburgh, PA Providence, RI Charleston, SC Greenville, SC Nashville, TN Chattanooga, TN Houston, TX Dallas, TX San Antonio, TX Austin, TX Fort Worth, TX Salt Lake City, UT Virginia Beach, VA Norfolk, VA Seattle, WA Spokane, WA Tacoma, WA Huntington, WV Charleston, WV Milwaukee, WI Madison, WI All locations →

Related services

Guides

How to Connect a Generator to Your House Safely →

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