How to Connect a Generator to Your House Safely

The three safe ways to use a generator

Extension cords to the appliances

This is the no-install option. Generac says a portable can run one or two plug-in appliances without any permanent changes to the house. Use heavy-duty cords made for outdoor use, and make sure each cord's wattage rating is higher than everything plugged into it.

The catch: cords can't reach anything hard-wired. No furnace, no well pump, no lights on a wall switch. And you end up with cords snaking through a cracked-open window, which lets exhaust in.

A manual transfer switch

A transfer switch is a small subpanel next to your main panel that moves chosen circuits from utility to generator. It can power hard-wired loads like the furnace, the well pump and lights. Generac's HomeLink 30-amp models come with 8 circuits and take up to 10, and the 50-amp models come with 10 and take up to 16.

Generac also sells switches with the cord connection built in. Its 30-amp switch covers one or two circuits on generators starting at 5 kW, and its whole-house 200-amp utility switch takes a 50-amp generator starting at 8 kW. More on these in manual transfer switches.

An interlock kit and an inlet box

An interlock is a metal plate on your main panel that lets only one breaker be on at a time: the utility main or the generator breaker. The generator feeds a back-fed breaker through an outdoor inlet. You get the whole panel, and you decide what runs by flipping breakers.

If your panel has a listed kit, the interlock is usually the cheapest way to get the whole house on generator power. If it doesn't, or you want fewer decisions in the dark, go with a transfer switch. Find your kit in generator interlock kits by panel brand.

What's in a generator hookup kit

Whichever route you pick, the parts list looks about the same:

• The interlock kit or the transfer switch.
• A two-pole breaker for the generator feed.
• An outdoor power inlet box. Generac's 30-amp kits use an L14-30 inlet and its 50-amp kits use a CS6377 inlet, both in NEMA 3R enclosures.
• A cord to match. Generac's 30-amp cord is 10 feet of 10/4 with L14-30 ends, and its 50-amp cord is 10 feet of 6/4 with a CS6364 connector and a 14-50 plug.
• Conduit and wire from the inlet to the panel. The HomeLink kits use 1-inch ENT on 30-amp models and 1-1/4-inch on 50-amp models.
• Battery-powered CO alarms in the house.

See the generator cord guide and generator inlet box basics to match the parts to your generator.

How the job goes

Using it in an outage

When the power comes back, reverse it: generator breaker off, main on, then shut the generator down.

Mistakes to avoid

• The "suicide cord." A male-to-male cord into a dryer or wall outlet puts generator power on the street side of your meter. It also leaves live prongs exposed. Don't.
• Forgetting the main. Without an interlock, nothing stops you from having both on.
• Running it in the garage with the door open. CPSC says never run a generator in a garage, shed or crawlspace, even with fans or open doors.
• Planning the inlet under a window. A 10-foot cord can't put the generator 20 feet from that window, so place the inlet where the generator can sit clear of openings.

When it's a pro job

The inlet and the panel work are always a pro job. Generac recommends a certified electrician for its transfer switches. Your part is choosing the setup, sizing the generator and knowing the outage routine cold.