A portable generator can keep your fridge, lights and furnace fan running during an outage, but it has to connect to your home safely. An interlock kit is a metal plate that fits on your breaker panel and stops the main breaker and the generator breaker from being on at the same time. That one job protects you, your neighbors and the utility workers who may be repairing the lines. Our five picks are all listed by their sellers for Square D QO or Homeline panels, so the first thing to check is your exact panel brand, series, amp rating and the space between the breakers. One kit is listed for 100 or 125 amp panels, and the other four for 150 or 200 amp panels. An interlock must be listed for your exact panel, and it should be installed by a licensed electrician, with any permit and inspection your local code requires. Below you will find what makes each kit different, plus a guide to choosing one safely.
Quick Comparison Table
| Product | Panel Fit | Breaker Spacing | Standout Feature |
|---|---|---|---|
| Natupal Generator Interlock Kit | Square D QO or Homeline, 150 or 200 amp | 1 3/8 inches | Steel plate; no extra control box or wiring needed |
| XMK Generator Interlock Kit | Square D QO or Homeline, 100 or 125 amp | 3/4 to 7/8 inches | Single handle, horizontal throw left to right |
| QYZZRS Generator Interlock Kit | Square D QO or Homeline, 150 or 200 amp | 1 3/8 inches | Includes 8 reminder labels and 2 start-up labels |
| SPZOCE Generator Interlock Kit | Square D QO or Homeline, 150 or 200 amp | 1 3/8 inches | Anodized aluminum alloy with polished edges |
| WHXMHRQ Generator Interlock Kit | Square D QO or Homeline, 150 or 200 amp | 1 3/8 inches | Steel kit with shoulder screws and hex nuts |
Our Picks: Best generator interlock kits for home panels reviews
Natupal Interlock Kit for 150 or 200 Amp Square D Panels
The Natupal kit is the plainest pick here. It is a steel plate listed for Square D QO or Homeline panels rated 150 or 200 amp, and it needs 1 3/8 inches between the main breaker and the generator breaker. The listing says it needs no extra control box or wiring, so the kit itself is just the plate and its hardware.
The box holds the plate, three shoulder screws, three hex nuts, a start-up procedure label, five reminder labels, two zip ties, the instruction bulletin and a 3/16 drill bit. The hardware is much like the other kits, so the main differences are the maker’s promise to mail a replacement if the kit ever fails and its steel build. It is only listed for the larger panel size, so a 100 or 125 amp panel needs the XMK instead. Have a licensed electrician confirm the fit to your panel before any drilling.
Pros:
- Made for 150 or 200 amp Square D QO and Homeline panels
- No extra control box or wiring needed
- Full set of screws, nuts, labels and a drill bit
- Maker promises a replacement if it fails
Cons:
- Does not fit smaller 100 or 125 amp panels
Verdict: Choose the Natupal kit if you have a 150 or 200 amp Square D QO or Homeline panel and want a simple plate with no extra control box, installed by a licensed electrician.
XMK Interlock Kit for Smaller 100 or 125 Amp Panels
The XMK kit is the one to look at if your panel is smaller. Every other kit in this list is made for 150 or 200 amp panels, but this one is made for Square D QO or Homeline panels rated 100 or 125 amp. It also lists a tighter gap, just 3/4 to 7/8 inches between the main breaker and the branch breakers, which is a different spacing from the other four kits.
It works as a single handle that throws horizontally from left to right. The listing says the design ensures the main breaker can never be on while the generator breaker is on. The kit includes the plate, three shoulder screws, three hex nuts, a matching drill bit, a start-up label, five reminder labels and two zip ties. Your electrician should read the instruction sheet closely before starting.
Pros:
- Only kit here for 100 or 125 amp panels
- Works in a tight 3/4 to 7/8 inch gap
- Single handle design keeps main and generator breakers from being on together
- Includes a matching drill bit and labels
Cons:
- Not for 150 or 200 amp panels
- Only suits one narrow panel size and spacing, so measure carefully
Verdict: Choose the XMK kit if your Square D QO or Homeline panel is rated 100 or 125 amp, because it is the only kit here listed for that size.
QYZZRS Interlock Kit With Extra Labels for Larger Panels
The QYZZRS kit stands out for its labels and its advice on getting the fit right. You get two generator start-up procedure labels and eight reminder labels, more than the five reminder labels in most other boxes. That matters if you want clear warnings near the panel for everyone in the house, not just the person who set it up.
It fits Square D QO and Homeline 150 or 200 amp panels with 1 3/8 inches of space between the main and generator breakers. The maker suggests attaching the screws to the plate first and doing a dry run, so you can line up the position before you drill. That small step helps avoid a misaligned plate that will not work. The box also has a drill bit, an instruction bulletin, screws and two zip ties. It suits households that want plenty of warning labels, and an electrician can do the dry run for you.
Pros:
- Eight reminder labels and two start-up labels
- Clear advice to do a practice fit first
- Fits 150 or 200 amp QO and Homeline panels
- Includes a drill bit and instruction bulletin
Cons:
- The advised dry run adds a little time to the install
Verdict: Choose the QYZZRS kit if you have a 150 or 200 amp Square D QO or Homeline panel and want extra warning labels and a built-in reminder to check the fit first.
SPZOCE Anodized Aluminum Interlock Kit for QO and Homeline
The SPZOCE kit is the only one here that tells you what the plate is made of. The listing says it is aluminum alloy with an anodized surface and polished edges, and it describes the kit as sturdy and durable. If you care about a clean, finished look inside your panel, this is the most appealing choice of the 150 or 200 amp group.
It fits Square D QO or Homeline panels with 1 3/8 inches between the main breaker and the generator breaker. The package includes the plate, three screws and nuts, a start-up label, five reminder labels, two zip ties, an instruction notice and a 3/16-inch steel drill bit. A detailed installation manual comes with it. If the kit does not meet your expectations, the seller says it will send a replacement. The trade-off is that the supplied data shows no function beyond the finish and material that the steel kits lack.
Pros:
- Anodized aluminum alloy with polished edges
- Includes a detailed installation manual
- Fits 150 or 200 amp QO and Homeline panels
- Seller offers a replacement if you are unhappy
Cons:
- Offers no feature beyond finish that the steel kits lack
Verdict: Choose the SPZOCE kit if you want an anodized aluminum plate with polished edges for a 150 or 200 amp Square D QO or Homeline panel.
WHXMHRQ Steel Interlock Kit for 150 or 200 Amp Panels
The WHXMHRQ kit is the most thoroughly explained of the group. Its listing describes the plate as a generator lockout kit and says it prevents utility power and generator power from being on at the same time. That is the whole point of an interlock, so it is helpful to see it stated clearly. It is made of steel and fits Square D QO and Homeline 150 or 200 amp panels at 1 3/8 inches of spacing.
Like the QYZZRS, it advises attaching the screws to the plate before installing and running a practice fit so the plate lines up. The box holds three shoulder screws, three hex nuts, a start-up label, five reminder labels, two zip ties, an instruction bulletin and a 3/16-inch drill bit. It does not offer anything the other 150 or 200 amp kits lack, so it makes the most sense when it is in stock and suits your panel.
Pros:
- Clear lockout design for utility and generator power
- Includes shoulder screws and hex nuts
- Practice-fit tip helps with alignment
- Fits 150 or 200 amp QO and Homeline panels
Cons:
- Little to set it apart from the other 150 or 200 amp kits
Verdict: Choose the WHXMHRQ kit if you want a steel lockout plate with clear safety language for a 150 or 200 amp Square D QO or Homeline panel.
How to Choose a Generator Interlock Kit for Your Panel
Match the Kit to Your Panel Brand and Series
Interlock plates are cut for a specific panel design, and the kit must be listed for your exact panel brand and model. Every kit here is listed by its seller for Square D QO or Homeline panels, and we only know what those listings state. Look at the label inside your panel door to confirm the brand and series, and have your electrician confirm the kit is approved for that panel. A plate made for another brand or series will not line up with your breakers, and forcing it is not safe.
Check Your Amp Rating
Panel size decides which plate you need. Four of these kits are for 150 or 200 amp panels, while the XMK kit is for 100 or 125 amp panels. Your main breaker is stamped with its amp rating, so you can read it right off the switch. Buying the wrong size is the most common way to end up with a kit that does not fit.
Measure the Breaker Spacing
The kits list the gap they need between the main breaker and the generator breaker. Most here ask for 1 3/8 inches, while the XMK asks for 3/4 to 7/8 inches. Measure your own panel before ordering, and make sure the spot where the generator breaker will sit lines up with that gap.
Look at What Comes in the Box
Most kits include a plate, three screws, three hex nuts, a drill bit, labels and zip ties. The label count differs: the QYZZRS has eight reminder labels, while most others have five. Labels matter because they tell anyone near the panel how to start the generator and which breaker to switch first.
Think About Material and Finish
Some kits use steel, and the SPZOCE uses anodized aluminum alloy with polished edges. Either can do the job, so finish is mostly about looks and your own preference. Do not pay extra for a feature you will never see once the panel door is closed.
Plan the Installation and Safety
A panel holds live power even when the main breaker is off, so the installation should be done by a licensed electrician, with a permit and inspection as your local code requires. Never backfeed your home by plugging a generator into a wall outlet, and use the interlock only with a properly installed generator inlet. Run the generator outdoors, well away from doors, windows and vents, and keep working carbon monoxide alarms inside your home. Follow the start-up procedure on the label every time.
Frequently Asked Questions
What does a generator interlock kit do?
It is a plate that slides between your main breaker and your generator breaker so only one can be on at a time. This stops generator power from flowing back out to the utility lines while the grid is also connected.
Will these kits fit any breaker panel?
No. These kits are listed for Square D QO or Homeline panels only. Check the brand, series and amp rating on your panel label before you order, and make sure the kit is listed for your exact panel.
Which kit is for a 100 or 125 amp panel?
The XMK kit is the one listed for 100 or 125 amp panels, with a breaker gap of 3/4 to 7/8 inches. The other four are for 150 or 200 amp panels.
Is it safe to run a generator indoors or in a garage?
No. A generator must run outdoors, away from doors, windows and vents, because it gives off carbon monoxide. Keep working CO alarms inside your home, and never power your house through a wall outlet.
Is a kit the same as a transfer switch?
Not quite. The listings call these a manual transfer method that lets a portable generator feed your panel, and the Natupal kit says it needs no extra control box or wiring. You operate the breakers by hand, using the start-up procedure on the label.
Should I hire an electrician?
Yes. The work happens inside a panel that can carry live power. A licensed electrician should install the kit, confirm it is approved for your panel and arrange any permit and inspection your local code requires.
Our Final Recommendation
Start with your panel, not the kit. If you have a 100 or 125 amp Square D QO or Homeline panel, the XMK is the only choice here. For a 150 or 200 amp panel, the QYZZRS suits anyone who likes extra warning labels, the SPZOCE suits anyone who wants an anodized aluminum plate, and the Natupal is a plain, simple option with a replacement promise. The WHXMHRQ is a solid steel option when its price and stock fit your plans. Whichever you pick, confirm it is listed for your exact panel, measure the breaker gap, and have a licensed electrician install it with any required permit and inspection. Run the generator outdoors and keep CO alarms working inside.