An interlock kit is sold per panel brand, series and main breaker position. Read the panel label first, then match a listed kit. The general guide covers legality, cost and the inspector’s checklist.
Generator interlock kit guide →A generator interlock kit only fits the panel it was made for. The four brands most houses have are Square D (QO and Homeline series), Siemens (including Murray and ITE), Eaton (BR and CH, the old Cutler-Hammer) and GE (PowerMark and related series). Within each brand the series, the amp rating and the position of the main breaker decide which kit, if any, is listed for your panel.
This page is the matching step. For whether interlocks are legal, what they cost and what the inspector checks, read the main interlock guide first.
Find your panel brand and series
- Open the panel door (the hinged door only) and read the label on its inside. It names the manufacturer and usually the series, the bus amp rating and the breaker types the panel accepts.
- Note the main breaker’s amp rating and where it sits: top or bottom of the panel, and whether the breakers are laid out vertically or horizontally.
- Photograph the label and the layout. A photo lets you check a manufacturer’s compatibility list or a seller’s fit checker without standing at the panel.
Safety: Stay behind the dead-front cover. Removing it exposes live parts: the service conductors feeding the main stay energized even with the main breaker off. Installing the kit, the backfeed breaker and the inlet is electrician work in most places, done under permit.
What to match, brand by brand
| Panel brand | Series to tell apart | What to check before ordering |
|---|---|---|
| Square D | QO and Homeline (HOM) | They are different series and take different kits. A Homeline kit does not fit a QO panel, and the reverse. |
| Siemens (also Murray and ITE) | Siemens and Murray load centres | Sold as one family by kit makers. Confirm the amp rating and that the main sits where the kit expects it. |
| Eaton | BR and CH (Cutler-Hammer) | BR and CH breakers are not interchangeable, and kits are made for one or the other. Read the breaker type on the label. |
| GE (and ABB) | PowerMark and related series | Kits vary by panel generation and by whether the main is vertical or horizontal. Match the exact panel model. |
The table tells you what to look for, not which kit to buy. The catalogue number that fits depends on your exact panel, so use the panel maker’s compatibility list or the seller’s fit checker, and treat a “universal” plate with suspicion. The two kits linked below are the ones we could tie to a named catalogue number for a named panel family. Check the fit before you order either.
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Square D HOMCGK2C interlock kit (Homeline panels) on Amazon →
Siemens ECSBPK01 interlock (Siemens/Murray panels) on Amazon →
When no kit fits your panel
Some panels have no listed kit: older or unusual load centres, panels where the main is centre-fed or side-mounted, and panels with no free slot for the backfeed breaker. Do not drill or modify a plate to make one fit. The alternatives are a manual or automatic transfer switch, which works with any panel, or replacing the panel, which an electrician can quote while they are there.
Some older panel designs have a known safety history, and an electrician should look at them before any generator connection is added. If yours is an old panel with no label you can read, ask for an assessment rather than guessing.
Cost and code in one paragraph
The kit itself is a small part of the bill; the breaker, the outdoor inlet, the cable and the electrician’s time make up most of it, and most places require a permit and an inspection. Acceptance is decided locally, so one call to the permit office settles it. The numbers and the inspector’s checklist are in the main guide, and the generator itself has to be 240 V and sized to your loads: see generator sizing.
Frequently Asked Questions
Can I use a Square D kit on a Siemens panel?
No. A kit is made for one manufacturer’s cover and breaker geometry. Even inside one brand, a kit for one series will not fit another.
How do I know if my Eaton panel is BR or CH?
Read the breaker type printed on the panel label and on the breakers themselves. Eaton sells both series and their breakers do not interchange, so the kit follows the series.
Does the main breaker amp rating matter?
Yes. Kits are listed for particular panel and main ratings, and the backfeed breaker and inlet are sized to the cord and the generator, not to the main. Your electrician sets those together.
Is an interlock kit a substitute for a transfer switch?
It is an alternative that meets the same requirement, that the generator and the utility cannot be connected at once, when a listed kit exists for your panel and your inspector accepts it. The main guide compares the two.