Best Generator Interlock Switch Kit Buying Guide for 2026
Finding the right generator interlock kit helps you safely backfeed power from a portable generator during outages. This guide compares five popular options, clarifying who each kit is best for and why. Suitable buyers include homeowners upgrading existing panels, DIY installers, and those needing a cost-effective backup power solution without a transfer switch.
| Product | Best For |
|---|---|
| Natupal Generator Interlock Kit (SD200A) | Square D QO/Homeline 150–200A panels; precise 1 3/8″ spacing |
| EXCELFU Generator Interlock Kit (Eaton BR/CH) | Eaton Cutler Hammer BR/CH series; versatile in 150–200A panels |
| XMK Generator Interlock Kit (Siemens/Murray) | Siemens/Murray 150–200A; flexible spacing 7/8″–1 1/4″ |
| SPZOCE Generator Interlock Kit (Eaton BR) | Eaton/Brummer BR system; straightforward installs |
| S7 Generator Interlock Kit (Homeline/QOM1/QOM2) | Square D Homeline 150–225A; no external panel needed |
Natupal Interlock Kit for Square D QO/Homeline Panels
Compatibility covers Square D QO and Homeline panels at 150 or 200 amps, with a precise 1 3/8 inch spacing between the main and generator breaker. This interlock kit directs generator power safely to a chosen circuit set, minimizing backfeed risks during outages. Best for homeowners using Square D equipment who want a straightforward installation without a full transfer switch.
Who it’s best for: DIY installers with Square D QO or Homeline panels seeking a cost-effective, non-transfer-switch backup solution.
Caution: Confirm panel model and space before purchasing to ensure the 1 3/8″ spacing matches your setup.
EXCELFU Interlock Kit for Eaton BR/CH 150–200A
This interlock kit is designed for Eaton Cutler Hammer BR series (and CH series with neutral) in 150–200 amp panels. It provides a safe, affordable means to backfeed a generator when storms or outages hit. Best for Eaton BR/CH panel users who want a compact, horizontal-right/left operation with a guaranteed separation between main and branch breakers.
Who it’s best for: Homes with Eaton panels needing a robust, economical backfeeding solution.
Caution: Check the exact model compatibility (BR/CH with plug-in neutral) and confirm the required spacing (1 1/4″–1 7/16″).
XMK Interlock Kit for Siemens or Murray Panels
Compatible with Siemens/Murray 150–200 amp panels, the kit spaces main and branch breakers from 7/8″ to 1 1/4″. It safely prevents both mains and generator power from feeding simultaneously, directing generator power to household circuits during outages. Best for Siemens/Murray users seeking flexible spacing and a straightforward install.
Who it’s best for: Homeowners with Siemens/Murray panels who value adjustable spacing for precise alignment.
Caution: Verify the exact model and spacing to avoid installation misalignment.
XMK Interlock Kit for Square D QO/Homeline 100–125A Panels
Designed for Square D QO or Homeline 100–125 amp panels, with 3/4″ to 7/8″ spacing between main and branch breakers. This kit emphasizes ease of use and cost-effectiveness for smaller service panels, making it a practical choice for smaller homes or apartments needing backup power without a full transfer panel.
Who it’s best for: Owners of 100–125A Square D panels who want a compact, low-cost backfeed option.
Caution: Suitable mainly for smaller panel sizes; double-check spacing and compatibility with your exact panel model.
S7 Homeline Interlock Kit for 150–225A Load Centers
The S7 interlock kit is tailored for Square D Homeline panels (QOM1/QOM2) and supports 150–225A load centers. It safely links a 2-pole generator breaker to the main, preventing simultaneous utility and generator power. Best for Homeline users who want a dedicated, integrated backup option without a separate transfer panel.
Who it’s best for: Homeline panel owners seeking a straightforward, integrated interlock solution.
Caution: Confirm panel model compatibility and required cover style (HOMCGK2C or similar) before purchase.
Buying Guide: Key Considerations for Generator Interlock Kits
- Panel compatibility: Verify panel brand (Square D, Eaton, Siemens, etc.), model family (QO, Homeline, BR, CH, BR/CH), and amp rating (100–225A).
- Breaker spacing: Most kits specify spacing between the main and generator breakers. Match the exact spacing to your panel for proper alignment.
- Installation complexity: Some kits come with drill bits and screws; others require precise alignment during assembly. Consider your comfort with electrical work and whether you’ll need professional help.
- Safety and backfeed control: A proper interlock prevents concurrent mains and generator power. Ensure the kit clearly addresses backfeed risks for your setup.
- Space and enclosure: Some kits require enough panel space or a particular cover style. Confirm there’s room for the interlock mechanism in your panel.
- Maintenance and replacement parts: Look for kits that include essential hardware and a straightforward replacement process if screws or bits wear out over time.
- Best use cases: For outages, interlock kits are ideal when you want a simpler backup path without a full transfer switch. If you require automatic switching during outages, a transfer switch may be more appropriate.
Frequently Asked Questions
- What is a generator interlock kit? It is a safety device that prevents simultaneous power from the utility grid and a portable generator by interlocking main and generator breakers.
- Do interlock kits require an electrician to install? Installation can be DIY if you have electrical experience and follow manufacturer instructions; many jurisdictions require a licensed electrician for code compliance.
- Can I use any interlock kit with my panel? No. Interlock kits are panel-specific. Verify brand, model, and amp rating before purchasing.
- Are interlock kits the same as transfer switches? No. Interlock kits do not automatically switch; they ensure safe manual transfer of generator power after you engage the main breaker.
- What spacing should I expect for a 150–200A panel? Spacing typically ranges from 1/4 inch to 1 3/8 inches, depending on the kit and panel type. Always verify exact spacing before purchase.
- Is a warranty provided with these kits? Warranties vary by seller; check product listings for specifics.
All five options above are designed to help you safely backfeed a generator when used with the corresponding panel families. Evaluate your panel brand, model, and required spacing to pick the kit that best matches your home’s electrical layout and backup power goals.