Generator interlock kit and inlet: what it costs installed
A generator interlock installed in SoCal typically costs $400 to $850 for the interlock alone, and $400 to $1,800 once you add an inlet box and cord. It lets a portable generator feed your panel without a transfer switch.
Typical SoCal range, October 2026
$400 to $1,800
interlock $400 to $850; inlet box and cord raise it. Starts from the published ranges listed under Sources. We moved the low or high end to fit Southern California, so this is an estimate, not a quote.
The cheap way to power a house from a portable generator is an interlock kit on the main panel. HomeGuide puts the installed interlock at about $400 to $850. With an inlet box on the outside wall and the cord, the typical SoCal range is $400 to $1,800 as of October 2026. This page is about that interlock job. A transfer switch is a different product with its own cost page, and a permanent generator has its own hookup page.
How the kit works and where it falls short is on the generator interlock kit page.
What you get for the money
The interlock is a sliding metal plate on the panel. It blocks the main breaker and the generator breaker from being on at the same time. That prevents backfeeding the utility lines during an outage. A generator inlet on the wall takes the cord from your portable unit. Power then feeds the whole panel, and you decide which breakers to switch on.
That whole-panel flexibility is the main reason people pick an interlock. You can run a refrigerator, a few lights and a furnace fan, then swap loads by hand.
What is in the $400 to $1,800
- Interlock kit: the plate and a generator breaker. About $400 to $850 installed per HomeGuide.
- Inlet box: a weatherproof inlet on the exterior wall. This is usually the largest add.
- Wire and conduit: from inlet to panel.
- Cord: a cord that matches your generator’s outlet.
- Permit and inspection.
The labor side follows HomeGuide’s figures for this kind of work: $50 to $130 an hour, a $75 call-out fee, and 2 to 4 hours for installation. SoCal rates run above the low end.
When an interlock is the wrong tool
- Panel not supported. Some panel brands and models do not have a listed interlock kit. Ask the electrician early.
- You want automatic power. An interlock is manual. See the transfer switch cost page.
- You want batteries. A home battery is a different category. The generator vs battery guide compares them.
- You need to protect only a few circuits. A critical-loads subpanel is another route.
Why SoCal homeowners ask about it
Power shutoffs during high-wind fire weather push people toward backup power. The PSPS explainer and the prep checklist show how those shutoffs work.
How the number builds up
HomeGuide’s labor figures are $50 to $130 an hour, a $75 call-out fee and 2 to 4 hours of work. That makes labor roughly $175 to $595. An interlock kit adds parts, which is how the installed price reaches $400 to $850. The inlet box, wire, conduit and cord are on top of that and explain most of the climb toward $1,800. If a quote lists only one lump sum, ask for the inlet and cord to be named.
Permit and inspection
An interlock changes the service panel, so it is permitted electrical work. Fees vary by city. See Los Angeles, Escondido or Fontana, or the San Bernardino County hub. The utility is not usually involved in a customer-side interlock.
How to compare quotes
- Is the interlock kit listed for your exact panel?
- Is the inlet box included, and at what height and location?
- Is the cord included, and what amperage?
- Is the permit in the price?
- Does the quote say the generator size it is designed for?
What is not included
The generator, fuel, a transfer switch, a critical-loads subpanel, trenching, and rebates. Generators themselves are a separate purchase.
What moves the price
| Factor | Effect | Range |
|---|---|---|
| Interlock alone vs full setup | HomeGuide lists interlock kits at about $400 to $850 for labor and materials; the inlet box and cord raise the total toward $1,800 | |
| Panel brand and model | An interlock kit must match the panel; some panels have kits and some do not | |
| Inlet box location | The distance from panel to the outside inlet changes wire and conduit length | |
| Generator size and cord | Higher-wattage generators need a heavier inlet and cord | |
| Electrician hourly rate | HomeGuide lists $50 to $130 an hour plus a $75 call-out fee, with 2 to 4 hours typical for transfer-switch type work |
Questions people ask
Is an interlock kit legal in California?
An interlock is a recognized way to connect a portable generator, but it must be installed correctly and permitted. Rules for the inlet, the breaker size and the interlock itself are in code, so a licensed electrician pulls a permit and the city inspects. Do not make your own backfeed cord.
Interlock or transfer switch: which is cheaper?
The interlock is usually cheaper. HomeGuide lists interlock kits at about $400 to $850, a manual transfer switch at $400 to $1,300 installed, and an automatic switch at $600 to $2,500. The interlock powers the whole panel but you choose loads by hand. A transfer switch limits you to chosen circuits.
What does an interlock actually do?
It is a metal plate that lets either the main breaker or the generator breaker be on, but not both. That keeps generator power from flowing back into the utility lines, which can hurt line workers. HomeGuide describes it as the way to connect a portable generator without a transfer switch.
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