Serving Southeast Michigan & Surrounding Areas
24-Hour Emergency Service Available
FAMILY OWNED | LICENSED & INSURED
Generator Interlock Kit Installation
An interlock on your panel and an inlet box outside, so a portable generator runs the furnace, fridge and sump pump with no cords through a window. Free quotes.
Get a Free Estimate
We call you back during office hours, Monday to Friday, 7 am to 5 pm.
Prefer to call? (734) 697-8477
Licensed and insured | Family owned | Free quotes | Office Mon to Fri, 7 am to 5 pm
3D Electric handles Generator Interlock Kit Installation for homeowners across Southeast Michigan who own a portable generator or plan to buy one. We are a family-owned, licensed and insured electrical contractor based in Belleville, with about two decades in the trade. Our Generator Interlock Kit Installation service puts an interlock on your main panel and a power inlet box on your outside wall, so the generator feeds your house through the panel instead of through extension cords.
An interlock kit costs less than a home standby system, and it lets you power the furnace, fridge, sump pump and lights in an outage. You still roll the generator out, start it and flip the breakers yourself. If you would rather have power come back on its own, compare it with our whole house generator installation options.
Lectro's tip
Write your panel brand and your generator's outlet type on a card and keep it by the panel; it speeds up the quote and helps in the dark.
What Generator Interlock Kit Installation Includes
A safe portable generator hookup has four parts. Each one is matched to your panel and to your generator.
The interlock kit on your main panel
The interlock is a metal plate or slide mounted on the panel cover. It lets the generator breaker turn on only when the main breaker is off. Utility power and generator power can never be connected at the same time.
A generator breaker
A two-pole breaker in the panel takes the generator power in. It is sized to the inlet and the cord, not to the biggest generator on the shelf.
The generator inlet box
A weatherproof power inlet box goes on an outside wall, near where the generator will sit. It is wired back to the generator breaker. In an outage you plug the cord in here, not into a window or a door gap.
The cord, labels and permit
The generator cord must match the generator's 240-volt outlet and the inlet. The panel gets clear labels, and the job is filed for an electrical permit and inspection.
How a Generator Interlock Works on Your Panel
Interlock kits are made for specific panel brands and models. The kit has to fit the cover and the breaker layout of your panel. Square D, Eaton, Siemens and GE panels each use their own kits.
When your panel has a listed kit
The generator breaker usually goes in the top slots on the opposite side from the main breaker. If those slots are full, we move circuits to make room.
When it does not
Some older or full panels have no listed interlock kit. Then the choice is a manual transfer switch or a new panel. We tell you which one makes sense at the quote visit. Our generator transfer switch installation page covers manual switches, and the interlock kit vs transfer switch guide compares the two side by side.
Never Backfeed Your House
A cord with a male plug on both ends feeds a generator backward through a dryer outlet or a wall outlet. It is illegal, and it is dangerous.
The bare prongs on the loose plug are live once the generator runs.
If the main breaker is on, generator power flows out through your meter and onto the utility lines.
A line worker repairing a wire they believe is dead can be electrocuted.
When utility power returns, the generator can be damaged or start a fire.
An interlock kit or a transfer switch is what stops backfeeding. That is why the panel connection is the most important part of the job.
Carbon Monoxide and Where the Generator Sits
A portable generator makes carbon monoxide, which you cannot see or smell. It can build up inside a house in minutes.
Keep it outside and away from openings
Run the generator outdoors only. Never run it in the garage, even with the door open, or in a basement or shed. Keep it away from windows, doors and vents, and follow the distance in your generator's manual.
Place the inlet box with that in mind
We pick an inlet spot where the generator can sit well away from openings and the cord still reaches. Put battery-powered or battery-backup CO alarms on every level of the house.
Matching the Inlet Box to Your Portable Generator
The inlet, the cord and the generator breaker are matched to the largest 240-volt outlet on your generator.
Generator outlet | Inlet and cord | Typical generator |
|---|---|---|
30 amp, 240 volt twist-lock | 30 amp inlet box and cord | Most mid-size portables |
50 amp, 240 volt | 50 amp inlet box and cord | Larger portables |
120 volt outlets only | Not a fit for a panel hookup | Small and some inverter generators |
What a portable generator can run
Most portables carry the furnace blower, fridge, freezer, sump pump, some lights and outlets, and on larger units a well pump. Central air, an electric range or an electric dryer usually need more than a portable can give.
With an interlock, every circuit in the panel is available. You choose what to turn on and keep the total under the generator's rating. Our guide on what size generator your house needs explains how to add up loads.
How the Installation Goes
Most interlock jobs follow the same order.
Free quote visit. We check the panel brand, open slots, the outside wall and the generator you own or plan to buy.
Written estimate. You get a detailed estimate in advance that lists the kit, breaker, inlet, cord and permit.
Permit. The work is filed with your city or township building department.
Install. The interlock and breaker go on the panel, the inlet goes on the wall and the two are wired together.
Inspection. The inspector checks the panel and the inlet.
Test and walkthrough. We test the switching steps with you so you know the order before an outage.
Floors are covered, work areas are contained, and we clean up before we leave.
Using the Hookup During an Outage
Roll the generator to its spot outside and plug the cord into the generator and the inlet box.
Start the generator and let it warm up for a minute.
Turn off the main breaker, then turn off the large circuits you do not need.
Slide the interlock over and turn on the generator breaker.
Turn circuits on one at a time, largest motor first.
When utility power returns, turn the generator breaker off, the main breaker on, then shut down and unplug.
Practice it once on a nice day, so the first time is not in the dark.
Permits and What Changes the Cost
An interlock and inlet box change your main panel, so the job usually needs an electrical permit and an inspection. Your township or city building department issues the permit; confirm current requirements for your address. Our generator installation permit guide explains the usual steps.
Cost factors
Whether a listed interlock kit exists for your panel model
Room in the panel for a two-pole breaker
Distance from the panel to the inlet box
A 30 amp or 50 amp inlet and cord
Permit and inspection fees in your community
An interlock kit is usually the lowest-cost way to connect a generator to the whole panel. If you are weighing it against a standby unit, see the whole house generator cost guide.
Interlock Kit or Standby Generator
A portable setup needs someone home who can haul, fuel and start the generator, often in snow or ice. If nobody is home during the day, or someone relies on medical equipment, price a standby unit too.
3D Electric installs and services Generac, Honeywell and Kohler home standby generators. See our Generac generator installation page for how an automatic system works.
Interlock kits in Belleville, Ann Arbor and Ypsilanti
We have local pages for interlock kit installation in Belleville, interlock kits for Ann Arbor homes and generator interlock installation in Ypsilanti. Elsewhere in Wayne, Washtenaw and Monroe counties, request a free interlock kit quote or call (734) 697-8477.
Related pages
Local details for Belleville and Van Buren Township
Local details for Ann Arbor homes
Local details for Ypsilanti homes
Automatic and manual switches
A plain side-by-side comparison
Permit and inspection steps
What changes the price of a standby system
Automatic home standby power
Frequently Asked Questions
It depends on your panel model, whether a listed kit exists for it, room for a two-pole breaker, the distance to the inlet box and the permit fees in your community. It usually costs much less than a standby generator system. We give you a detailed written estimate after a free quote visit.
A listed interlock kit made for your panel, installed under an electrical permit and inspected, is an accepted way to connect a portable generator. Requirements can vary by community, so check with your building department. Backfeeding through a dryer or wall outlet is never legal.
The job means working inside your main panel, adding a breaker and running wire to an outdoor inlet, and it usually needs a permit and inspection. Rules on homeowner permits vary by community. We recommend a licensed electrician for panel work.
Interlock kits are made for specific panel brands and models. Many common panels have a listed kit, but some older or full panels do not. In that case a manual transfer switch or a new panel is the safe choice, and we tell you which at the quote.
Match the inlet to the largest 240-volt outlet on your generator. Most mid-size portables have a 30 amp twist-lock outlet, and larger ones have a 50 amp outlet. Generators with only 120-volt outlets are not a good fit for a panel hookup.
With an interlock, every circuit is available, but you can only run what the generator can carry. Most portables handle the furnace, fridge, sump pump, lights and outlets. Central air and electric ranges usually need a larger standby generator.