Generator cords, inlet boxes and interlock kits (2026)

To run house circuits from a portable generator, three parts work together: a generator cord from the generator's twist-lock outlet, a power inlet box on the outside wall, and either a transfer switch or a panel interlock kit inside. This page compares the cords, inlet boxes, cord-and-inlet sets and interlock kits we list, on amps, length and what they fit. The transfer switch kits are on our transfer switch page. Every spec is from the product listing, read on the date in each card's notes; we haven't installed these ourselves.

By Tom Calder · Updated November 8, 2026 · 11 products, all price-tracked

Generator cords and inlet boxes compared for US households

Our picks

Best 30-amp generator cord 4.2

Generator to inlet box

Champion 100395 cord

Generator power cord, 25 ft, 30 A · 30 A · 7,500 W · L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box

Generator to inlet box or switch, 25 ft

Researched

Check price →

Best cord and inlet box set 4.2

Both parts in one box

CircleCord 10 ft cord and inlet box

Generator cord and inlet box set, 30 A · 30 A · 7,500 W · 10 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a manual transfer switch or interlocked panel by a licensed electrician

Cord and inlet box in one set

Researched

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Best power inlet box 4.3

The outside socket the cord plugs into

Connecticut Electric EGSPI30

Power inlet box, 30 A, NEMA 3R · 30 A · 7,500 W · NEMA L14-30 inlet; wired to a transfer switch or interlocked panel by a licensed electrician, with a generator cord from the generator

30A inlet for a manual transfer setup

Researched

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Best interlock kit 3.9

Panel plate, fitted by an electrician

Natupal SD200A interlock

Generator interlock kit (panel mounted) · 200 A · Panel: Square D QO or Homeline, 150 or 200 amp · Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician

Fits only the listed panel

Researched

Check price →

All 11 compared

Show

Part	What it is	Amps	Generator size (max)	Circuits	Generator hookup	Price
1. Connecticut Electric EGSPI30 30-Amp Power Inlet Box with Hinged Door, NEMA 3R Best power inlet box Power inlet box, 30 A, NEMA 3R · 30 A · 7,500 W · NEMA L14-30 inlet; wired to a transfer switch or interlocked panel by a licensed electrician, with a generator cord from the generator 30A inlet for a manual transfer setup 4.3	Power inlet box, 30 A, NEMA 3R	30 A	7,500 W	—	NEMA L14-30 inlet; wired to a transfer switch or interlocked panel by a licensed electrician, with a generator cord from the generator	Check price →
Our verdict Our verdictResearched A 30-amp NEMA 3R power inlet box with a hinged door, for generators up to 7,500 running watts. It is wired in by a licensed electrician and a generator cord runs from the generator to this inlet, never to a wall outlet. No cord is included. Best for 30A inlet for a manual transfer setup Good NEMA 3R hinged door ETL listed Rated for generators up to 7,500 running watts Worth knowing No cord included 30A only Must be installed by a licensed electrician Who shouldn't buy it: Don't buy it if you want to wire it yourself or have a 50A generator: installation is for a licensed electrician and this is a 30A inlet.
2. Champion 100395 25-Foot 30-Amp 250-Volt Generator Power Cord (L14-30P to L14-30R) Best 30-amp generator cord Generator power cord, 25 ft, 30 A · 30 A · 7,500 W · L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box Generator to inlet box or switch, 25 ft 4.2	Generator power cord, 25 ft, 30 A	30 A	7,500 W	—	L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box	Check price →
Our verdict Our verdictResearched A 25 ft 30-amp generator cord from Champion for a manual transfer switch. The cord only ever runs from the generator to an inlet box or transfer switch, never to a wall outlet. The inlet box and switch are installed by a licensed electrician. Best for Generator to inlet box or switch, 25 ft Good Champion-branded, 25 ft 10 gauge, weather-resistant jacket 1-year warranty Worth knowing Needs an inlet box or transfer switch already installed 30A only Listing's conductor count is inconsistent Who shouldn't buy it: Don't buy it if your generator has no L14-30R outlet or your switch is 50A: this is a 30A L14-30 cord.
3. CircleCord 10-Foot 30 Amp Generator Cord and Inlet Box (GEC43010FT) Best cord and inlet box set Generator cord and inlet box set, 30 A · 30 A · 7,500 W · 10 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a manual transfer switch or interlocked panel by a licensed electrician Cord and inlet box in one set 4.2	Generator cord and inlet box set, 30 A	30 A	7,500 W	—	10 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a manual transfer switch or interlocked panel by a licensed electrician	Check price →
Our verdict Our verdictResearched A 10 ft 30-amp cord and a pre-drilled inlet box in one set. The box is wired in by a licensed electrician, and the cord only ever runs from the generator to the inlet box, never to a wall outlet. The short cord means the generator sits close to the box. Best for Cord and inlet box in one set Good Cord and inlet box together Rubber-plugged knockouts, no drilling Storage bag and cord organizer Worth knowing 10 ft cord is short 30A only Must be installed by a licensed electrician Who shouldn't buy it: Don't buy it if you need a longer cord or a 50A hookup: this is 10 ft and 30A.
4. RVINGPRO 30 Amp Generator Cord 25 FT and Pre-Drilled Power Inlet Box Generator cord and inlet box set, 30 A · 30 A · 25 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a transfer switch or interlocked panel by a licensed electrician Cord and inlet box, 25 ft 4.1	Generator cord and inlet box set, 30 A	30 A	—	—	25 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a transfer switch or interlocked panel by a licensed electrician	Check price →
Our verdict Our verdictResearched A 25 ft 30-amp cord and pre-drilled inlet box sold as a combo kit. The box is wired in by a licensed electrician, and the cord only ever runs from the generator to the inlet box, never to a wall outlet. The listing gives few specs. Best for Cord and inlet box, 25 ft Good Cord and inlet box together 25 ft cord ETL listed Worth knowing Few specs in the listing 30A only Must be installed by a licensed electrician Who shouldn't buy it: Don't buy it if you need wattage or model details first: the listing gives none.
5. PlugSaf 50-Foot 30 Amp Generator Cord, 10 AWG, NEMA L14-30P to L14-30R Generator power cord, 50 ft, 30 A · 30 A · 7,500 W · L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box Long run from generator to inlet 4.0	Generator power cord, 50 ft, 30 A	30 A	7,500 W	—	L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box	Check price →
Our verdict Our verdictResearched A 50 ft four-wire 30-amp generator cord with twist-lock ends and an ETL listing. The cord only ever runs from the generator to an inlet box or transfer switch, never to a wall outlet. The inlet box and switch are installed by a licensed electrician. Best for Long run from generator to inlet Good 50 ft length 4 conductors, 10 AWG ETL listed Worth knowing Needs an inlet box or transfer switch already installed 30A only No warranty stated in the listing Who shouldn't buy it: Don't buy it if you need the generator close to the house or a 50A connection: this is a 50 ft, 30A cord.
6. POWGRN 20-Foot 30 Amp Generator Extension Cord, L14-30P to L14-30R, STW, ETL Listed Generator power cord, 20 ft, 30 A · 30 A · 7,500 W · L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box Short 30A generator cord 4.0	Generator power cord, 20 ft, 30 A	30 A	7,500 W	—	L14-30P plug to L14-30R connector, generator to a manual transfer switch or inlet box	Check price →
Our verdict Our verdictResearched A 20 ft four-wire 30-amp twist-lock generator cord with a cord organizer. The cord only ever runs from the generator to an inlet box or transfer switch, never to a wall outlet. The inlet box and switch are installed by a licensed electrician. Best for Short 30A generator cord Good 4 conductors, 10 gauge ETL listed Cord organizer included Worth knowing Needs an inlet box or transfer switch already installed 30A only No model number in the listing Who shouldn't buy it: Don't buy it if you need more than 20 ft or a 50A cord: this is 20 ft and 30A.
7. VEVOR 30 Amp Generator Cord and Power Inlet Box, 15 FT, NEMA L14-30P to L14-30R Generator cord and inlet box set, 30 A · 30 A · 7,500 W · 15 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a transfer switch or interlocked panel by a licensed electrician Cord and inlet box, 15 ft 4.0	Generator cord and inlet box set, 30 A	30 A	7,500 W	—	15 ft L14-30P to L14-30R cord from the generator to the inlet box; the box is wired to a transfer switch or interlocked panel by a licensed electrician	Check price →
Our verdict Our verdictResearched A 15 ft 30-amp cord and a pre-drilled weatherproof inlet box. The box is wired in by a licensed electrician, and the cord only ever runs from the generator to the inlet box, never to a wall outlet. Best for Cord and inlet box, 15 ft Good Cord and inlet box together Pre-drilled holes Rated -4 to 140 F Worth knowing 30A only Listing's conductor count is inconsistent Must be installed by a licensed electrician Who shouldn't buy it: Don't buy it if you need a 50A hookup: this is a 30A L14-30 set.
8. Natupal SD200A Generator Interlock Kit for Square D QO or Homeline 150 or 200 Amp Panels Best interlock kit Generator interlock kit (panel mounted) · 200 A · Panel: Square D QO or Homeline, 150 or 200 amp · Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician Fits only the listed panel 3.9	Generator interlock kit (panel mounted)	200 A	—	Panel: Square D QO or Homeline, 150 or 200 amp	Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician	Check price →
Our verdict Our verdictResearched An interlock kit for Square D QO or Homeline, 150 or 200 amp. It is a plate that stops the main breaker and the generator breaker being on together. It fits only the panels listed, must be fitted by a licensed electrician, and the electrician should confirm the local inspector accepts a third-party kit for your panel. Best for Fits only the listed panel Good Designed for the listed panel Kit parts and labels included 1 3/8 in spacing between main and generator breaker Worth knowing Fits only the panels listed Must be fitted by a licensed electrician Inspector approval of a third-party kit needs confirming Who shouldn't buy it: Don't buy it if your panel is not exactly the one listed or your inspector does not accept third-party kits: it fits only Square D QO or Homeline, 150 or 200 amp.
9. Natupal ITE-200A Generator Interlock Kit for ITE, Gould, Murray, Siemens and Thomas and Betts 150 or 200 Amp Panels Generator interlock kit (panel mounted) · 200 A · Panel: ITE, Gould, Murray, Siemens, Thomas and Betts, 150 or 200 amp · Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician Fits only the listed panel 3.8	Generator interlock kit (panel mounted)	200 A	—	Panel: ITE, Gould, Murray, Siemens, Thomas and Betts, 150 or 200 amp	Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician	Check price →
Our verdict Our verdictResearched An interlock kit for ITE, Gould, Murray, Siemens, Thomas and Betts, 150 or 200 amp. It is a plate that stops the main breaker and the generator breaker being on together. It fits only the panels listed, must be fitted by a licensed electrician, and the electrician should confirm the local inspector accepts a third-party kit for your panel. Best for Fits only the listed panel Good Designed for the listed panel Panel brands and breaker spacing stated in the listing 1 1/4 in spacing between main and generator breaker Worth knowing Fits only the panels listed Must be fitted by a licensed electrician Inspector approval of a third-party kit needs confirming Who shouldn't buy it: Don't buy it if your panel is not exactly the one listed or your inspector does not accept third-party kits: it fits only ITE, Gould, Murray, Siemens, Thomas and Betts, 150 or 200 amp.
10. HUBRV Generator Interlock Kit for Eaton Cutler Hammer BR Series 150 and 200 Amp Panels Generator interlock kit (panel mounted) · 200 A · Panel: Eaton Cutler Hammer BR series, 150 and 200 amp · Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician Fits only the listed panel 3.8	Generator interlock kit (panel mounted)	200 A	—	Panel: Eaton Cutler Hammer BR series, 150 and 200 amp	Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician	Check price →
Our verdict Our verdictResearched An interlock kit for Eaton Cutler Hammer BR series, 150 and 200 amp. It is a plate that stops the main breaker and the generator breaker being on together. It fits only the panels listed, must be fitted by a licensed electrician, and the electrician should confirm the local inspector accepts a third-party kit for your panel. Best for Fits only the listed panel Good Designed for the listed panel Kit parts and labels included 1 7/16 to 1 1/4 in spacing between main and generator breaker Worth knowing Fits only the panels listed Must be fitted by a licensed electrician Inspector approval of a third-party kit needs confirming Who shouldn't buy it: Don't buy it if your panel is not exactly the one listed or your inspector does not accept third-party kits: it fits only Eaton Cutler Hammer BR series, 150 and 200 amp.
11. XMK GK-007 Generator Interlock Kit for Square D QO or Homeline 100 or 125 Amp Panels Generator interlock kit (panel mounted) · 100 A · Panel: Square D QO or Homeline, 100 or 125 amp · Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician Fits only the listed panel 3.8	Generator interlock kit (panel mounted)	100 A	—	Panel: Square D QO or Homeline, 100 or 125 amp	Mechanical plate on the panel so the main breaker and the generator breaker cannot both be on; a generator cord then runs from the generator to an inlet box wired to that breaker, installed by a licensed electrician	Check price →
Our verdict Our verdictResearched An interlock kit for Square D QO or Homeline, 100 or 125 amp. It is a plate that stops the main breaker and the generator breaker being on together. It fits only the panels listed, must be fitted by a licensed electrician, and the electrician should confirm the local inspector accepts a third-party kit for your panel. Best for Fits only the listed panel Good Designed for the listed panel Kit parts and labels included 3/4 to 7/8 in spacing between main and branch breakers Worth knowing Fits only the panels listed Must be fitted by a licensed electrician Inspector approval of a third-party kit needs confirming Who shouldn't buy it: Don't buy it if your panel is not exactly the one listed or your inspector does not accept third-party kits: it fits only Square D QO or Homeline, 100 or 125 amp.

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The rule that matters most

An inlet box, transfer switch or interlock kit is wiring work: OSHA says never to attach a generator to a building's electrical system unless a qualified electrician has properly installed it with a transfer switch, so have a licensed electrician fit it, with any permit your area needs. Never power house wiring by plugging a generator into a wall outlet, whatever cord is used: CPSC calls that backfeeding, says it is extremely dangerous, and warns it is an electrocution risk to utility workers and neighbors. If you only need a refrigerator and lamps, heavy-duty outdoor extension cords run straight from the generator, and you need none of this.

Before you buy

Match the plug to the outlet.

Many home backup generators have a 120/240V L14-30R (30-amp, four-prong twist-lock) outlet; the cords here have an L14-30P plug on the generator end and an L14-30R connector that plugs into the inlet box. A generator with only a 14-50R (50-amp) outlet needs a 50-amp cord and inlet box instead; we don't list one yet, though the Generac HomeLink 9854 kit on our transfer switch page includes a 50-amp inlet box.

Length: the generator has to stand outdoors, at least 20 feet from windows, doors and attached garages (Ready.gov).

CPSC says to use cords long enough to keep it far away from windows, doors and vents. Measure from where it will stand to the inlet box before you buy.

Check the cord's rating and gauge on its listing, and inspect it for cuts or damage before each use; OSHA says never to use frayed or damaged cords.

Inlet box: a weather-rated (NEMA 3R) box with a male L14-30 inlet, mounted outside and wired by a licensed electrician to a transfer switch or to the generator breaker of an interlocked panel.

Interlock kits are a metal plate on the breaker panel that stops the main breaker and the generator breaker being on together.

Each fits only certain panel brands and sizes: check yours, and have your electrician confirm your local inspector accepts a third-party kit for your panel.

Transfer switch or interlock?

A transfer switch kit powers a set number of chosen circuits; an interlock lets you pick any breakers in the panel, which makes it easier to overload the generator. Your electrician can advise on which suits your home.

Fit carbon monoxide alarms with battery backup on every level of your home before you run the generator.

How we choose

We verify every product's specifications against at least two independent sources, re-check its US price and stock on a schedule where we can track it automatically, and cross-check safety-relevant claims against official guidance. Every review is labeled Researched or Used and reviewed by us: where we've bought a product, or been sent it free, and used it ourselves, its review says which; where we haven't, our verdict is a considered spec-and-evidence comparison, not a hands-on test. When two products are close, commission can decide which one we pick. A clearly better product always wins. Read our full methodology →

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Guides that go with this

Portable generator safety: where to run it, carbon monoxide and cords

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Power outage checklist: what to do before, during and after

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Carbon monoxide poisoning: symptoms, sources, alarms and what to do

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Common questions

What cord do I need to connect a generator to my house?

For a generator with an L14-30R outlet, a 30-amp cord with an L14-30P plug and an L14-30R connector, long enough for the generator to stand outdoors and well away from the house, plugged into a power inlet box a licensed electrician has wired to a transfer switch or interlocked panel.

Can I plug a generator into a dryer outlet or wall outlet?

No. CPSC says never to power house wiring by plugging a generator into a wall outlet, a practice known as backfeeding, which it calls extremely dangerous and an electrocution risk to utility workers and neighbors. It also bypasses some of the household circuit protection.

Is a generator interlock kit legal?

Rules are local. An interlock kit is wiring work on your panel: have a licensed electrician fit it, and ask them to confirm your local inspector accepts the kit for your panel. OSHA says never to attach a generator to a building's electrical system unless a qualified electrician has installed it with a transfer switch.

Do I need a 30-amp or 50-amp cord?

Match the generator's outlet and your inlet box. A 30-amp L14-30 setup covers generators with an L14-30R outlet; a generator whose 240V outlet is a 14-50R needs a 50-amp cord and inlet box.

How long should a generator cord be?

Long enough for the generator to stand outdoors and at least 20 feet from windows, doors and attached garages, as Ready.gov says. Measure the distance from that spot to your inlet box.

Sources (3)

CPSC: Portable generator safety alert (CO, wet weather, backfeeding)
OSHA: Using portable generators safely, fact sheet OSHA 3286transfer switch, clear space, wet conditions
Ready.gov: Power outagesgenerators outdoors, at least 20 feet from windows, doors and attached garages