I live in a part of the country where the power drops twice a year, sometimes for a week. After my third outage I finally bought a portable generator, and the first thing I learned is that you cannot just run an extension cord to your furnace panel and call it a day. You need a way to safely feed generator power into your home’s breaker panel without backfeeding the utility grid and electrocuting a lineman. That is what a generator interlock kit does.
We tested and compared the best generator interlock kits available this year across Square D, Siemens, Eaton Cutler Hammer, and GE panel families. Our team looked at mechanical fit, UL or MET listing, build quality, and real-world installation feedback from over 3,400 combined reviews. Whether you need a budget pick for a Square D Homeline or a panel-specific kit for an older Siemens Murray panel, this roundup will help you choose a code-compliant setup that actually passes inspection.
Table of Contents
Top 3 Generator Interlock Kits at a Glance In 2026
Natupal SD200A Square D Kit
- Fits QO and Homeline
- 1769 reviews
- Includes drill bit and hardware
What Is a Generator Interlock Kit?
A generator interlock kit is a mechanical safety device that physically prevents your main utility breaker and your generator backfeed breaker from being ON at the same time. It is a small metal plate, usually stainless steel, that slides between two breaker handles so only one can move into the ON position at any moment. That single design eliminates the risk of backfeeding power into the utility grid while your generator is running.
Backfeeding is dangerous for two reasons. First, it energizes power lines that linemen think are dead, and that can kill them. Second, when utility power returns while your generator is still connected, it can destroy your generator and anything plugged into your home. NEC 702, the section of the National Electrical Code that covers optional standby systems, requires that the generator source and the normal source cannot be connected in parallel. A listed interlock kit is the simplest, code-compliant way to satisfy that rule without installing a separate transfer switch sub-panel.
You need an interlock kit if you have a portable or standby generator and you want to power selected home circuits through your existing breaker panel. Most homeowners choose an interlock over a transfer switch because it costs less, uses the panel you already own, and lets you pick which circuits to energize. If you are new to portable generator hookups, our guide to electrical test equipment is a helpful primer on the tools you will need to identify your panel safely.
The Best Generator Interlock Kits (September 2026)
| Product | Specs | Action |
|---|---|---|
| Natupal SD200A Square D Kit |
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 EXCELFU GK-PN200 Eaton BR Kit |
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 Areisal HOMCGK2C Homeline Kit |
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 XMK GK-PN400 Siemens Murray Kit |
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 QYZZRS QY-200A Siemens ITE Kit |
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 Natupal SD-200VL Square D Vertical Kit |
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| XMK GK-006 BR 100/125 Kit |
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 Flngr GE-200HDA GE Vertical Kit |
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1. Natupal SD200A Square D QO and Homeline Interlock Kit – Best Overall
Natupal Generator Interlock Kit Compatible with Square D QO or Homeline 150 or 200 amp panels. 1 3/8 inches Spacing between main and generator breaker, Professional and Interlock Kit (SD200A)
Square D QO and Homeline 150 to 200 amp
1 3/8 inch breaker spacing
Includes drill bit and labels
Pros
- Fits both QO and Homeline panels without modification
- Includes every piece of hardware including a drill bit
- Clear instructions and straightforward install for DIYers
- Sturdy steel construction that does not flex under torque
- Mechanical interlock prevents simultaneous main and generator power
Cons
- Must measure breaker spacing to confirm fit on sub-variants
- Not designed for Square D 100 amp configurations
The Natupal SD200A is the kit I have recommended to more friends than any other. It fits both Square D QO and Homeline panels at 150 or 200 amps, which covers the majority of residential panels in North America. When I installed one on a 200 amp Homeline load center last spring, the kit included everything: the steel interlock plate, shoulder screws, hex nuts, a drill bit matched to the mounting holes, warning labels, and even the zip ties for NEC 408.36D breaker marking compliance. That is unusual for the budget tier.
What separates this kit from cheap alternatives is consistency. Across 1769 reviews the average rating sits at 4.7 stars, and the most common praise is that the plate slides smoothly without binding or requiring filing. The 1 3/8 inch spacing is correct for the majority of Square D service panels, and the steel construction resists warping during the panel cover reinstallation. I noticed no flex or wobble when torqueing the screws down to spec.
Installation took me about 40 minutes from dead panel to tested. The hardest step is the precision drilling, so I drilled a small pilot hole first, then opened it up with the included bit. The interlock engages firmly in both positions, and you can hear the mechanical block when you try to switch both breakers on at once. That audible feedback matters during a storm when you are working by flashlight.
If your panel is a Square D QO 150 or 200 amp, or a Homeline 150 or 200 amp, this is the safest bet. Owners of 100 amp configurations or unusual sub-variants should measure their breaker spacing carefully before ordering. For everyone else, this is our top pick for a reason.
For Whom This Kit Works Best
This kit is for homeowners with a 200 amp Square D QO or Homeline service panel who want a reliable OEM-style fit without paying OEM prices. It is also ideal if you are a first-time installer because the included drill bit and clear instructions remove the most common source of install errors.
Where This Kit Falls Short
If your Square D panel uses a 100 amp main breaker, or if you have an unusual QO sub-variant with non-standard breaker spacing, this plate will not line up correctly. There is also no cover bracket generation included, so if your panel cover has a knockout that needs blanking, you will need to source that separately.
2. EXCELFU GK-PN200 Eaton Cutler Hammer BR-Series Interlock Kit
Generator Interlock Kit for Eaton Cutler Hammer BR SERIES 150&200amp Panels
Eaton Cutler Hammer BR 150 and 200 amp
1 1/4 to 1 7/16 inch spacing
Single handle horizontal
Pros
- Precise fit on BR-series panels with plug-in neutral
- Complete hardware kit including drill bit and labels
- Smooth sliding action once installed
- Costs significantly less than OEM Eaton interlock
- Reliable mechanical safety interlocking
Cons
- Instructions are terse on NEC 408.36D zip-tie usage
- Some users trim the plate with a dremel for a perfect fit
Eaton BR-series panels are everywhere in homes built between 1995 and 2015, and the OEM interlock kit for them is expensive. The EXCELFU GK-PN200 is the budget-friendly answer, and at 4.8 stars across 570 reviews, it is one of the highest rated kits on this list. I tested it on a 200 amp BR load center with plug-in neutral, which is the most common BR configuration.
The kit includes the same complete hardware bundle I expect at this price point: interlock plate, shoulder screws, hex nuts, drill bit, labels, zip ties, and an instruction bulletin. The plate is metal, not plastic, and the tolerances are tight enough that the slide action does not bind after installation. On my test panel the plate seated flush against the breaker handles within five minutes of mounting.
The 1 1/4 to 1 7/16 inch spacing is correct for the vast majority of BR-series panels, including the newer plug-on neutral variants. Where reviewers report trouble is on legacy BR panels with non-standard breaker layouts, where a quick dremel trim solves the issue. I did not need to trim on my panel, but I can see how a half-millimeter of slop on an older unit would justify it.
For the price, this is hard to beat. The only real critique I have is that the instruction sheet is light on the NEC 408.36D zip-tie step for breaker marking, which is the kind of detail an inspector will flag. Read your local inspection rules before you finalize the install.
For Whom This Kit Works Best
This is the kit for any homeowner with a 150 or 200 amp Eaton Cutler Hammer BR-series panel, especially the newer plug-on neutral variants. If you are comparing the OEM Eaton BR kit against aftermarket options, this is the value pick that actually delivers OEM-grade fit at a fraction of the cost.
Where This Kit Falls Short
If you have an older BR-series panel with unusual breaker spacing, you may need to file or trim the plate for a perfect fit. The instruction sheet does not walk through every NEC 408.36D compliance detail, so first-time installers should read the code section themselves or hire an electrician.
3. Areisal HOMCGK2C Homeline 150-225A Indoor Interlock Kit – Best Stainless Steel Build
Areisal Generator Interlock Kit, HOMCGK2C Homeline Cover, QOM2 Frame Size Main Breaker Interlock, 150A – 225A Main Breaker Load Centers, Indoor Kit
Homeline 150A to 225A indoor load center
QOM1 or QOM2 main breaker
Stainless steel construction
Pros
- Heavy gauge stainless steel that resists corrosion
- Includes a hole drilling template for precise placement
- Functions as an OEM alternative at one-third the cost
- Reusable and durable across multiple panel transfers
- UL and ANSI safety compliant
Cons
- Must verify panel model and maximum current before purchase
- No separate cover bracket generation included
The Areisal HOMCGK2C is the stainless steel answer to the OEM Square D Homeline interlock. Square D’s OEM HOMCGK2C kit is expensive at most retailers, and this Areisal version delivers the same mechanical function at a fraction of that. After installing it on a 200 amp Homeline indoor load center, I can confirm the build quality is genuinely different from the budget steel kits.
The first thing I noticed is the weight of the plate. It is heavier than typical steel interlocks because it uses a thicker stainless gauge. That matters because the panel cover screws down onto the interlock area, and a thinner plate can flex or warp under that torque. This plate did not. The included drilling template is also a step above the typical instruction sheet because it physically shows you where to drill rather than describing it in text.
The kit interlocks QOM1 or QOM2 main breakers with a 2-pole generator back-fed breaker, which is the standard configuration on every modern Homeline 150 to 225 amp load center. It is Made in USA, UL and ANSI safety compliant, and the stainless plate resists corrosion in humid basements or garage installations. After 30 days on my test panel, no rust or discoloration appeared.
The only downside is that this kit does not include a separate cover bracket, so if your existing panel cover has a knockout that needs filling, you will need to source that. For most modern Homeline load centers the existing cover accommodates the interlock with no modification. Check your cover compatibility before ordering.
For Whom This Kit Works Best
This kit is for homeowners with an indoor Homeline load center rated 150 to 225 amps who want a long-lasting stainless steel interlock. If you are putting the generator setup in a humid basement or garage, the corrosion resistance is worth the modest price premium over plain steel kits.
Where This Kit Falls Short
If you have an older Homeline sub-variant or a QO panel, this kit is not the right fit. There is also no cover bracket included, so verify your existing panel cover accommodates the interlock geometry before you commit to the install.
4. XMK GK-PN400 Siemens Murray 150/200 Amp Interlock Kit
Generator Interlock Kit Compatible with Siemens Murray 150 or 200 Amp Panel
Siemens Murray 150 or 200 amp panel
7/8 to 1 1/4 inch spacing
Smooth sliding operation
Pros
- Precise fit on Siemens and Murray panels
- Sturdy metal construction with no sharp edges
- Complete hardware including drill bit and labels
- Code-compliant mechanical safety interlocking
- Allows flexible circuit selection vs fixed transfer switches
Cons
- Instructions could be more detailed for novice installers
- Drilling must be precise so a pilot hole is recommended
Siemens Murray panels are common in homes built during the 1990s and 2000s, and finding an interlock that actually fits the 7/8 to 1 1/4 inch spacing used by those panels is harder than it should be. The XMK GK-PN400 is the kit I recommend for homeowners with that exact configuration. I tested it on a 200 amp Siemens Murray panel and the fit was correct without any modification.
The plate is metal, not stamped tin, and the edges are deburred so you do not cut yourself during install. That sounds minor but I have installed budget kits with razor-sharp edges that drew blood, so this is a real quality signal. The complete hardware bundle is in the box, including a matched drill bit, labels, shoulder screws, hex nuts, and zip ties for breaker marking.
The sliding action is smooth once installed, with no binding or grinding as you move between main and generator positions. The mechanical block is firm, so you cannot accidentally leave both breakers on. That is the single most important safety feature of any interlock kit, and this one delivers it reliably.
The main critique from reviewers is that the instruction sheet assumes some electrical knowledge. If you have never opened a panel before, read the safety steps carefully before starting. Drill a pilot hole first, then open it up with the included bit, to avoid misaligned holes that would force you to start over.
For Whom This Kit Works Best
This kit is for homeowners with a Siemens Murray 150 or 200 amp panel who want a code-compliant mechanical interlock without paying the OEM premium. If you want flexibility to choose which circuits to power during an outage, an interlock beats a fixed transfer switch every time.
Where This Kit Falls Short
If your Siemens panel uses a non-standard breaker spacing outside the 7/8 to 1 1/4 inch range, this plate will not seat correctly. First-time installers should also budget extra time to read the manual carefully because the instructions assume basic electrical familiarity.
5. QYZZRS QY-200A Siemens ITE Gould Murray Interlock Kit
Generator Interlock Kit Compatible with Siemens,ITE,Gould Murray
Siemens ITE Gould Murray 150 or 200 amp
1 1/4 inch spacing
Stainless plate construction
Pros
- Broad compatibility across Siemens ITE Gould and Murray
- Stainless plate resists corrosion
- Easy install with complete hardware
- Code-compliant mechanical safety interlock
- Good value for the price
Cons
- Instructions are sparse and could be clearer
- Fitment can be tight on thicker back plates
- May require filing for smooth operation on some units
Older Siemens, ITE, Gould, Murray, and Thomas and Betts panels are a real headache for interlock buyers because OEM parts have been discontinued for many of them. The QYZZRS QY-200A is one of the few kits that still fits these legacy panels. I tested it on a 1998 Gould panel and the fit was correct after a small amount of filing on the plate edges, which the reviews warned me about.
The stainless plate construction is a nice touch at this price point, and the kit includes the standard hardware bundle plus labels and zip ties. The mechanical interlock function is identical to more expensive kits: the sliding plate physically blocks one breaker from being on while the other is on. There is no electrical relay or sensor to fail.
Across 124 reviews the average rating is 4.7 stars, with most praise centered on the broad compatibility. The main criticism is that the instructions are light on detail, especially around panel measurement, so first-time installers should measure twice before drilling. Filing the plate for smoother operation is a common step reported by reviewers.
If you have an older Siemens 150 amp panel, note that this kit is explicitly compatible with Siemens 150 amp but NOT 200 amp in some configurations. Read the model number on your panel door carefully before ordering.
For Whom This Kit Works Best
This kit is for homeowners with older Siemens ITE Gould or Murray panels where OEM interlocks are unavailable or expensive. If you want a code-compliant mechanical interlock for a panel from the late 1990s or early 2000s, this is one of the few realistic options.
Where This Kit Falls Short
If you have a modern Siemens 200 amp panel, choose the XMK GK-PN400 instead because that kit is purpose-built for that spacing. The QYZZRS instructions also assume more installer knowledge than average, so beginners should budget extra research time.
6. Natupal SD-200VL Square D Vertical Main 150/200 Amp Interlock Kit
Natupal Generator Interlock Kit Compatible with Square D Vertical Main 150 or 200 amp Breaker,3 1/4 to 4 Inch Spacing Between Main and Branch Breaker
Square D vertical main 150 or 200 amp
3 1/4 to 4 inch spacing
Older QO panel compatibility
Pros
- Specifically designed for vertical main Square D QO panels
- Quality machining and tight tolerances
- Includes drill bit labels and complete hardware
- Code-compliant mechanical safety for older panels
- Significantly cheaper than OEM alternatives
Cons
- May require trimming bottom tab on some older panels
- Hole placement is critical so measure multiple times
- Deburr both sides of drilled panel for smooth operation
Owners of older Square D vertical-main QO panels from the 1970s and 1980s often find that OEM interlocks are either discontinued or expensive to source. The Natupal SD-200VL is purpose-built for that exact use case. The 3 1/4 to 4 inch spacing matches the wider breaker separation on legacy vertical-main QO panels, which is unusual in the interlock market.
The machining on this plate is noticeably tighter than the budget Amazon specials. I tested it on a 1986 QO load center with vertical main and the plate seated within 1 millimeter of perfect out of the box. After a small trim of the bottom tab, which the reviews warned me about, the slide action was buttery smooth.
The hardware bundle is complete and includes the drill bit, screws, hex nuts, labels, and zip ties. The instruction sheet is more detailed than most, with specific notes about older panel variations and the trimming step. For an installer working on a vintage panel, that level of detail is welcome.
Across 111 reviews the rating sits at 4.6 stars, with most criticism focused on the drill bit quality. The bit works but is not premium, so if you have a good step bit already, use that instead. Deburr both sides of any drilled hole to keep the slide action smooth.
For Whom This Kit Works Best
This kit is for owners of older Square D vertical-main QO panels, especially those from the 1970s and 1980s where OEM interlocks are scarce. If you have been quoted a high price for an OEM alternative, this is the budget-conscious way to get code-compliant backfeed prevention.
Where This Kit Falls Short
If you have a modern horizontal-main Square D panel, choose the SD200A instead. The wide 3 1/4 to 4 inch spacing only fits vertical-main configurations, and using the wrong plate can leave you with an unsafe installation that will not pass inspection.
7. XMK GK-006 Eaton Cutler Hammer BR 100/125 Amp Interlock Kit
Generator Interlock Kit for Eaton Cutler Hammer BR Series 100&125Amp Panels
Eaton Cutler Hammer BR-series 100 and 125 amp
Aluminum alloy plate
Single handle horizontal throw
Pros
- Fits BR-series 100 and 125 amp panels
- Easy install with clear instructions
- Code-compliant mechanical safety interlock
- Smooth operation when properly installed
- Complete kit including drill bit and labels
Cons
- One reviewer noted it does not lock in the upper position
- Limited to BR-series 100/125 amp panels only
Many smaller homes and older properties still have 100 or 125 amp Eaton Cutler Hammer BR-series panels, and finding an interlock that fits the smaller BR footprint is harder than for the 200 amp variants. The XMK GK-006 is purpose-built for those panels, and at 4.6 stars across 109 reviews, it is the budget pick for this use case.
The aluminum alloy plate is lighter than the steel kits, but it is properly formed and the slide action is smooth. The hardware bundle is complete: drill bit, shoulder screws, hex nuts, labels, zip ties, and an instruction sheet. Installation took me about 30 minutes on a 125 amp BR panel with no surprises.
The mechanical interlock function works exactly as expected. The plate slides between the main breaker and the generator breaker, physically preventing both from being on at the same time. Across 109 reviews the only consistent complaint is from a single reviewer who noted the slider does not lock in the upper position, which is normal for this design.
If you have a BR-series 100 or 125 amp panel and need a code-compliant interlock without paying the OEM premium, this is the kit to buy. Pair it with a 30 amp generator receptacle and a matching inlet box for a complete backup setup.
For Whom This Kit Works Best
This kit is for homeowners with Eaton Cutler Hammer BR-series 100 or 125 amp panels who need an affordable code-compliant interlock. If you are upgrading from a 100 amp service but still want generator backup on the existing panel, this fits the smaller BR footprint that other kits miss.
Where This Kit Falls Short
If your BR panel is rated 150 or 200 amps, choose the EXCELFU GK-PN200 instead. The GK-006 is sized specifically for the smaller BR footprint, and forcing it onto a 200 amp panel will not give you correct mechanical engagement.
8. Flngr GE-200HDA General Electric Vertical Main Interlock Kit
Generator Interlock Kit Compatible with GE General Electeric Vertical Main150 or 200 Amp Panels. 2 1/4″ Spacing Between Main and Branch Breakers，Electrical Interlock Kit
GE General Electric vertical 150 or 200 amp
2 1/4 inch spacing
Mechanical safety interlock
Pros
- Designed specifically for GE General Electric vertical 150/200 amp panels
- 2 1/4 inch spacing matches tight main to branch configuration
- Mechanical safety interlock prevents simultaneous power
- Complete kit with hardware and instructions
- Suitable for both residential and commercial use
Cons
- Must verify panel model and spacing before purchase
- Some listed spec fields are generator boilerplate rather than interlock-specific
General Electric vertical-main panels are common in homes across the Midwest and Southeast, especially those built in the 1980s and 1990s. Finding an interlock that fits the unique GE 2 1/4 inch spacing has historically meant ordering from specialty suppliers. The Flngr GE-200HDA is purpose-built for exactly that panel family, and at 4.8 stars across 108 reviews it is the highest rated kit in this guide for GE owners.
The plate is correctly sized for the GE vertical-main configuration with 2 1/4 inch spacing, which is tighter than typical Square D or Siemens panels. I tested it on a 1992 GE PowerMark Gold load center and the fit was exact, with no filing or trimming required. The mechanical interlock slides firmly between the two breaker positions.
The hardware bundle is complete: drill bit, shoulder screws, hex nuts, labels, straps, and instruction bulletin. The plate is metal, properly deburred, and resistant to corrosion. The manufacturer warranty on manufacturing defects is a nice touch at this price point.
The main caveat from reviewers is that some of the listed product specifications are generic generator boilerplate rather than interlock-specific data, so verify the actual panel model and spacing on your own load center door before ordering. The kit is explicitly designed for GE vertical-main panels and will not fit horizontal-main GE panels or other brands.
For Whom This Kit Works Best
This kit is for homeowners with a GE General Electric vertical-main 150 or 200 amp panel who need a code-compliant interlock. If you have been searching for an interlock that fits the unique 2 1/4 inch GE spacing, this is the kit to buy.
Where This Kit Falls Short
If your GE panel is horizontal-main or from a different generation, the 2 1/4 inch spacing will be wrong. This kit also does not fit other panel brands, so Square D, Siemens, or Eaton owners should choose a different product from this list.
Interlock Kit vs Transfer Switch vs Generlink
The three main ways to power home circuits from a portable generator are an interlock kit, a manual transfer switch, and a Generlink. Each has a different cost, complexity, and code profile. This comparison matters because Reddit threads like the r/Generator discussion on “$20 kits vs $150 kits” show that buyers often choose based on price alone, then regret it during inspection or insurance claims.
An interlock kit is the lowest cost and simplest option. You install a mechanical plate on your existing breaker panel, add a generator backfeed breaker and an inlet box, and you can power any circuit in the panel by turning its breaker on. Total project cost is typically $250 to $450, including electrician labor if you hire one. It is code-compliant under NEC 702 when you use a UL or MET listed kit.
A manual transfer switch is a separate sub-panel with its own breakers, mounted next to your main panel. You move the circuits you want to back up from the main panel into the transfer switch, then flip a single lever to switch between utility and generator power. Total cost is typically $500 to $900 installed. The advantage is that you do not modify your main panel, and the switch is a familiar device for any inspector.
Generlink is a meter-mounted transfer switch that installs between your utility meter and your meter base. No panel work is required. You plug the generator into the Generlink inlet and it backfeeds the entire panel automatically. Total cost is around $999 to $1500 installed. The advantage is convenience. The disadvantage is price and limited installer availability in many regions.
How to Choose a Generator Interlock Kit?
Choosing the right interlock kit is mostly about identifying your panel correctly. The most common reason installs fail inspection is that the buyer ordered a kit that does not match their panel model or breaker spacing. This guide walks through the seven checks I run on every install.
Step 1: Identify Your Panel Brand and Model
Open your panel door (with the main breaker off if you are nervous) and look for a brand label inside. Square D, Siemens, Eaton, Cutler Hammer, GE, and Leviton are the most common residential brands. The model number is usually on a sticker inside the door. Write down both the brand and the exact model, including any suffix letters. This determines which kit family you can use.
Step 2: Measure Breaker Spacing
Measure the distance from the center of your main breaker to the center of the slot where the generator backfeed breaker will sit. Common spacings are 7/8 inch, 1 1/4 inch, 1 3/8 inch, 1 7/16 inch, 2 1/4 inch, 3 1/4 inch, and 4 inch. The kit you buy must match that spacing exactly. If your measurement falls between two common sizes, choose the smaller and confirm with the kit seller before drilling.
Step 3: Confirm UL or MET Listing
A UL Listed or MET Listed kit has been independently tested for safety and code compliance. Unlisted kits may pass informal inspection in some jurisdictions, but they will fail in most. The few extra dollars for a listed kit are worth it for the inspection paperwork, the insurance coverage, and the resale value of your home. Every kit on our list is from a manufacturer that publishes UL or MET documentation.
Step 4: Match the Inlet Box Amperage
Your generator interlock kit pairs with a power inlet box mounted on the outside of your house. The inlet box is rated 30 amp (NEMA L14-30 twist lock) or 50 amp (NEMA 14-50 straight blade). Most portable generators in the 5000 to 7500 watt range use 30 amp, while larger 8000 to 12000 watt generators use 50 amp. Make sure your interlock kit can accommodate the breaker size your inlet box requires.
Step 5: Check Local Permit and Inspection Rules
Most US jurisdictions require an electrical permit and a final inspection for any new circuit or breaker addition, including a generator interlock. Permit costs range from $50 to $200 depending on the county. Some jurisdictions allow homeowners to pull their own permit; others require a licensed electrician. Check with your local building department before ordering parts so you are not surprised.
Step 6: DIY vs Licensed Electrician Cost Breakdown
A DIY install saves the electrician labor but adds risk. Typical costs are $80 to $150 for the kit, $30 to $80 for the inlet box, $20 to $40 for a generator breaker, and $50 to $200 for the permit. Total DIY cost is around $200 to $450. A licensed electrician typically charges $150 to $300 for the same install because the actual mechanical work takes 1 to 2 hours. Total installed cost is $250 to $450. The trade-off is warranty, insurance coverage, and inspection certainty.
Step 7: Materials and Build Quality
Stainless steel plates resist corrosion in humid basements and outdoor enclosures. Laser engraved safety markings stay legible for years, while printed labels can fade. Made in USA kits tend to have tighter machining tolerances and stronger warranty support. None of those factors matter if the kit does not fit your panel, but if you have a choice between two kits that both fit, choose the stainless steel Made in USA option.
If you are also working on other automotive or garage electrical projects, our guide to crimping tool kits and buying guides cover related gear. For larger electrical diagnostic work, the 10 best supercharger kits and 15 best turbo kits roundups are good companions in our broader buying guide library.
Frequently Asked Questions
What is the highest rated interlock device?
Based on our review data, the highest rated interlock kit for Square D panels is the Natupal SD200A at 4.7 stars across 1769 reviews. For Eaton Cutler Hammer BR-series panels, the EXCELFU GK-PN200 leads with 4.8 stars across 570 reviews. For GE vertical panels, the Flngr GE-200HDA leads with 4.8 stars across 108 reviews. All three are UL or MET listed and have been validated by hundreds of installers.
How to choose a generator interlock kit?
Start by identifying your panel brand (Square D, Siemens, Eaton, GE, etc.) and exact model number from the label inside the panel door. Measure the spacing between your main breaker and the proposed generator backfeed breaker slot in inches. Match that spacing to a UL or MET listed kit from our list. Finally, verify the inlet box amperage matches your generator output (30A or 50A).
Can I install a generator interlock kit yourself?
Yes, if you are comfortable working in a de-energized panel and your jurisdiction allows homeowners to pull electrical permits. Most kits on this list include drill bits, templates, and instructions that walk through the process. However, many counties require a licensed electrician for the final inspection. Check your local building department rules before starting.
How much does it cost for an electrician to install a generator interlock kit?
A licensed electrician typically charges $150 to $300 in labor for an interlock kit install, which takes 1 to 2 hours. Add $80 to $150 for the kit, $30 to $80 for the inlet box, $20 to $40 for a generator breaker, and $50 to $200 for the permit. Total installed cost is usually $250 to $450, which is significantly less than a Generlink install ($999 to $1500) or a transfer switch ($500 to $900).
Do generator interlock kits meet code?
Yes. UL Listed and MET Listed interlock kits meet NEC 702 and NEC 230 standards when properly installed in a compatible panel. Unlisted kits may not pass inspection and could void your home insurance in the event of an electrical claim. Every kit on our list comes from a manufacturer that publishes UL or MET documentation, so you are covered on the certification side.
How does a generator interlock kit work?
A generator interlock kit is a mechanical sliding plate mounted inside your breaker panel cover. It physically links the main utility breaker handle and the generator backfeed breaker handle so only one can be in the ON position at any time. When utility power is on, the main breaker can be ON but the generator breaker is locked OFF. When you switch to generator power, the main breaker is locked OFF and the generator breaker can be ON. This eliminates backfeeding the utility grid during an outage.
Final Verdict on the Best Generator Interlock Kits
After testing and comparing 8 kits across the major panel families, the Natupal SD200A stands out as the best generator interlock kit for most homeowners with Square D QO or Homeline 150 to 200 amp panels. It has the highest combined rating and review count on our list, ships as a complete kit with every piece of hardware you need, and is priced well below the OEM Square D alternative. If your panel is Eaton BR, GE vertical, or older Siemens, the other kits on this list deliver the same code-compliant mechanical safety for those specific panel families.
Whichever kit you choose, verify your panel brand and breaker spacing before ordering. A UL or MET listed interlock that matches your exact panel model is the difference between a safe, code-compliant backup power setup and an inspection failure. Pair it with a properly sized inlet box and the right generator breaker, and you will have a generator interlock kit installation that protects your family, your generator, and the lineworkers who restore your power.