Generator cord: 30-amp vs 50-amp

The cord is the only piece of a portable hookup you should be shopping without an electrician. The inlet on the wall, the interlock, and the breaker are a listed system. The cord has to match both ends of that system: the receptacle on the generator, and the inlet on the house. Buy the wrong one and you either stand in the yard with two plugs that will not mate, or you start looking at adapters that should not exist.

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What does the cord cost?

HomeGuide’s 2026 transfer-switch guide puts a heavy-duty generator cord at $30 to $350. Cost to Renovate’s 2026 page puts the inlet itself at $50 to $150 and the run from the panel to the outside at $100 to $350, inside a typical whole hookup of $700 to $2,000. Extra length on that page is on the order of $30 to $50 per extra 10 feet, which is the electrician’s cable in the wall, not the yellow cord on Amazon. Same neighborhood, different wire.

HomeGuide: generator transfer switch installation cost

Cost to Renovate: generator transfer switch

A 25-foot 30-amp L14-30 cord is usually the low-to-middle of HomeGuide’s $30 to $350 band. A 25-foot 50-amp cord with the locking house connector is the upper half. If a listing is $19 and claims 50 amps, keep walking.

The inlet box page is the legal hookup. This page is the cord you put in the cart after the inlet shape is already decided.

What do 30-amp and 50-amp actually mean?

A 30-amp, 240-volt circuit is 7,200 watts on paper (30 × 240). A 50-amp, 240-volt circuit is 12,000 watts. Those are the inlets. Your generator may be stickered 7,500 running watts and still only have a 30-amp outlet, which means the cord and the inlet are the bottleneck even if the engine could do more into a bigger receptacle.

The well pump page is the reminder that starting watts are not running watts. A 30-amp inlet will not grow because the pump nameplate is scary. If the electrician already set a 50-amp inlet, buy a 50-amp cord. Do not “make do” with a 30-amp cord and a cheater.

Look at the generator’s receptacle, not the brochure’s watt chart:

• L14-30 is a 4-prong twist-lock. Very common on 7,000 to 9,000 watt portables. House inlets for this size are usually L14-30 too.
• 14-50 is a 4-prong straight blade, same family as many ranges and EV chargers. Common on bigger portables.
• SS2-50 / CS6364 is a 50-amp locking connector. A lot of 50-amp house inlets use this, while the generator still has a 14-50 straight blade. The cord then has different ends: 14-50P on the generator, SS2-50R (CS6364) on the house.

Photograph both ends before you order. “50-amp generator cord” on Amazon is not one product.

Which cord matches a 30-amp inlet?

You want L14-30P to L14-30R, 10-gauge, 4-conductor (that’s 10/4), jacket rated for outdoor use (SJTW or STW), UL or ETL listed. 25 feet is the length that lets the generator sit away from windows and still reach a garage-wall inlet. 10 feet is cheaper and parks the exhaust against the siding. 50 and 100 feet add voltage drop and coil weight you will hate at midnight.

Twist-lock matters. A straight 30-amp plug that can tug out in the rain is the wrong family.

Skip the “fan” cords that turn an L14-30 into four household 5-15/5-20 outlets, if the plan is to feed the house inlet. Those are for tools on a jobsite. Feeding the panel through an inlet wants the same 4-prong locking shape on both ends. A cord into a dryer outlet is still the thing that can backfeed the street. The inlet page already said that.

Which cord matches a 50-amp inlet?

First confirm the inlet. If it is a twist-lock 50-amp (SS2-50 / CS6364), a 14-50 to 14-50 range cord will not go in. If it is a 14-50 straight inlet, a locking CS6364 cord will not go in.

A common generator-to-house 50-amp cord is 14-50P (straight, generator) to CS6364 / SS2-50R (locking, house), 6-gauge class conductors, 25 feet, listed.

If both ends are 14-50 straight, buy that cord instead. Do not force a locking connector with a hammer. Do not use an adapter pyramid so a 30-amp generator can “use” a 50-amp inlet. The inlet breaker is 50 amps. The generator outlet is 30. The weak link is the machine, and the adapter will not invent copper.

How long, and how thick?

10 AWG is the 30-amp language. 6 AWG (or 6/3 + 8/1 on some 50-amp STW cords) is the 50-amp language. If a 50-amp, 25-foot listing says 10-gauge, that is a 30-amp cord in a 50-amp photo.

Shorter is better electrically. Longer is better for carbon monoxide, because the generator wants to sit outside, away from windows, and downhill of the house if you can. The inlet belongs on an exterior wall. The cord is how you keep 25 feet between the muffler and the people. Indoor running is how CO kills. The queued carbon monoxide page is the rest of that lecture; the short version is a plug-in alarm in the house and the machine in the yard.

Do not daisy-chain three 25-foot cords because the generator is across the driveway. Have the electrician move the inlet, or park closer.

What should not be in the cart?

A 12-gauge orange home-center cord. A dryer pigtail. A 30-to-50 adapter “just for tonight.” A cord with no listing mark. A 100-foot 10-gauge run you found because it was on sale.

If you do not have an inlet yet, do not buy a 50-amp cord “to be ready.” Buy the cord the day you can photograph the inlet and the generator outlet together. The electrician who installs the inlet should tell you L14-30 or 14-50 / SS2-50 in the bid. Put that string in the Amazon search.

The rest of the hookup kit (inlet, interlock, oil, cover) still lives on the queued portable-generator hookup tools list. This page is only the copper between the machine and the wall.

What does a worked example look like?

House A. 7,500-watt portable, L14-30 twist-lock on the panel of the generator, 30-amp inlet already on the garage. The cord is 25 feet of 10/4, L14-30 both ends, listed. Paper limit is 7,200 watts at 240 volts. The fridge and the furnace blower fit. The well pump on the other page may not start. No adapter.

House B. 12,000-watt portable with a 14-50 straight receptacle, 50-amp locking inlet the electrician put next to the meter. The cord is 14-50P to CS6364, 25 feet, 6-gauge class. Paper limit is 12,000 watts. That is the setup that can take a well pump if the nameplate LRA still fits, which you check before the storm, not during it.

House C. Same 7,500-watt L14-30 generator, and someone already installed a 50-amp inlet “for later.” There is no honest 30-to-50 cord. The fix is a 30-amp inlet, or a generator that actually has a 50-amp receptacle. An adapter that feeds a 50-amp inlet from a 30-amp outlet asks the inlet breaker to protect wire the generator never supplied.

Park the generator on the driveway, pull the cord in a straight-ish run, keep the exhaust pointed away from the garage door, and do not run the cord under a sash. If the only way to reach the inlet is through a window, the inlet is in the wrong place.

How do I decide this week?

1. Photograph the generator receptacle and the house inlet, then write the NEMA name (L14-30, 14-50, SS2-50) on both.
2. Match amperage to the inlet you actually have: 30-amp cord for L14-30, 50-amp cord for a 50-amp inlet, never a mix through an adapter.
3. Pick 25 feet unless the inlet is on top of the generator; skip 50 and 100 feet unless the electrician already ran that far.
4. Confirm 10/4 and a listing mark on 30-amp cords, and 6-gauge-class conductors plus a listing mark on 50-amp cords.
5. Buy L14-30P to L14-30R for the 30-amp twist-lock pair, or the 14-50P to CS6364 cord if that is what the 50-amp inlet really is.
6. If there is no inlet yet, stop shopping cords and send the inlet box page to the electrician. The cord is the last part, not the first.