Interlock Kit Panel Compatibility

This is the single most useful page on the site for anyone taking the interlock route, because the information is scattered across listings and getting it wrong means a plate that will not install.

Step one: identify your panel

1. 1Turn off nothing yet — you are only reading labels and measuring, not touching conductors. If you are not comfortable opening the cover, have your electrician do this step.
2. 2Read the brand on the panel door or the label inside: Square D, Eaton, Cutler-Hammer, Siemens, Murray, GE, Homeline.
3. 3Read the main breaker's amperage — it is printed on the breaker handle: 100, 125, 150 or 200 A.
4. 4Identify the series where it matters: Square D panels are QO or Homeline; Eaton panels are Type BR or Type CH. The label states it.
5. 5Measure the spacing between the main breaker and the nearest branch breaker, in the direction the main breaker's handle throws.

For Siemens there is one extra question: plug-on-neutral or not. Plug-on-neutral panels have breakers that clip directly to a neutral bar rather than using pigtail wires. It changes the required spacing, and the XMK GK-009 listing publishes both figures for exactly this reason.

The published compatibility table

The short answer

Quick picks

#	Product	Best for	Score	Price
1	Eaton BRMIKBR Factory Interlock Kit 100-125A Pay the premium for this one: a factory interlock with a stated NEC Article 702 basis removes both the fit risk and the inspection risk.	Factory kit that satisfies inspectors	8.9/10★★★★★	$84.00
2	XMK Interlock Kit — Siemens/Murray 100A The best-documented interlock kit here on the question that actually matters — it tells you the spacing for both Siemens neutral variants.	100A Siemens, both neutral types	8.3/10★★★★★	$19.99
3	XMK Interlock Kit — Square D QO/Homeline 100/125A The correct kit for an older, smaller Square D panel — and the published spacing range means you can confirm fit before ordering.	Smaller Square D panels	8.2/10★★★★★	$19.99
4	SPZOCE Interlock Kit — Square D QO/Homeline 150/200A The cheapest correct way to connect a generator to the whole panel, provided your panel is a Square D QO or Homeline with the exact spacing stated — measure first.	Square D QO and Homeline, 150-200A	8.5/10★★★★★	$26.99
5	EXCELFU Interlock Kit — Eaton BR 150/200A The affordable option for an Eaton BR panel, with the spacing published so you can verify fit — but check whether your inspector wants the factory kit.	Eaton / Cutler-Hammer BR panels	8.0/10★★★★★	$19.99
6	SPZOCE Interlock Kit — Eaton BR 100/125A A complete, cheap kit for a smaller Eaton BR panel, as long as your main and generator breaker positions can be adjacent.	Smaller Eaton BR panels	8.0/10★★★★★	$26.99
7	SPZOCE Interlock Kit — Siemens/Murray 150/200A The main third-party option for a Siemens or Murray panel — identify your plug-on-neutral variant before ordering.	Siemens and Murray panels	7.8/10★★★★★	$26.99

#ad Prices as of October 5, 2026; they may have changed since. Scores are our editorial judgment from published specifications, not test results — how we pick. How we are funded.

The layout requirement people miss

Spacing is not the only geometry that matters. SPZOCE's Eaton BR 100/125 A kit publishes a requirement for adjacent main and generator breakers — the two have to sit next to each other for the plate to interlock them.

If your panel's available slots are not adjacent to the main breaker, that may mean rearranging breakers, which adds to the install. Worth checking at the same time as the spacing: look at where there is a free double-pole slot, and whether it is next to the main.

If your panel is not in the table

Square D, Eaton and Siemens/Murray cover a large majority of US residential panels, but not all of them. GE, Zinsco, Federal Pacific and other older panels may have no interlock kit available at all — and in the case of Zinsco and Federal Pacific, a panel replacement is a conversation worth having with an electrician for reasons unrelated to generators.

If no kit exists for your panel, a transfer switch is the route. It costs more in hardware, works with any panel, and is a listed product nobody argues about — Champion publishes UL 1008 certification on its 50 amp unit.

When to buy the factory kit instead

If a factory interlock exists for your panel, it eliminates both risks in one purchase: fit is certain because the manufacturer made both parts, and the code basis is stated — Eaton's BRMIKBR listing says it meets National Electrical Code Article 702 requirements.

It costs roughly four times a third-party plate, which on a job that already involves an electrician and a permit is usually a small fraction of the total. If your panel is an Eaton Type BR 100-125 A, buy it.