L14-30R outlet
The L14-30R is the standard 30-amp, 120/240-volt twist-lock receptacle found on most mid-size portable generators. It carries up to 7,200 watts through a single cord and is the usual connection point for a transfer switch or interlock.
The naming decodes as: L = locking (the plug twists in and cannot vibrate loose), 14 = the 125/250 V four-wire configuration (two hots, neutral, ground), 30 = 30 amps, R = receptacle. The matching plug is an L14-30P.
Because it delivers both 120 V legs and 240 V, the L14-30 can feed an entire small panel through a generator inlet. A generator with only 120 V outlets (L5-30, 5-20) cannot run 240 V appliances like well pumps or dryers regardless of wattage.
| Configuration | 4-wire, 125/250 V, 30 A — two hot legs, neutral, and equipment ground |
|---|---|
| Maximum through the connector | 7,200 VA at 240 V; 3,600 VA per 120 V leg |
| Continuous-load ceiling | 24 A / 5,760 W at 240 V, applying the 80% rule for loads running three hours or more |
| Matching plug and cord | L14-30P plug on 10 AWG four-conductor cord (10/4), typically 25 or 50 ft |
| Defining standard | ANSI/NEMA WD 6, which fixes the blade geometry for every NEMA configuration |
| Not interchangeable with | 14-30R (straight-blade dryer outlet), L14-20R, L5-30R, or TT-30R |
Decoding the name and the four wires
L means locking. 14 is the NEMA configuration number for a four-wire 125/250 V device. 30 is the ampere rating. R is receptacle; P is plug. The four contacts are X and Y — the two hot legs, with 240 V between them and 120 V from each to neutral — plus W for neutral and G for ground. Both voltages come out of one connector, which is precisely why this is the standard generator outlet rather than a 240 V-only device like an L6-30.
The locking action is not a luxury. The plug inserts and twists roughly a quarter turn, and curved blades then ride behind the receptacle face so vibration or a tugged cord cannot back it out. A straight-blade connector working loose under 30 A of load arcs, and arcing at that current melts the connector and can start a fire. It is also why adapting an L14-30 down to a homemade straight-blade convenience cord is a bad idea even when the gauge is right.
Having a neutral is what makes the connector useful for a house. Because W is present, the two hot legs can carry unequal 120 V loads and the imbalance returns on the neutral conductor. A connector without a neutral cannot feed a panel at all, since almost everything in a house is a 120 V load referenced to neutral. The fact that neutral and ground are separate pins here is also the reason the floating-versus-bonded-neutral question exists at all.
The 7,200-watt ceiling and how to reach it
30 A × 240 V = 7,200 VA, and that is the connector’s limit regardless of what the generator behind it can produce. A 9,500 W generator fitted with only an L14-30 outlet delivers 7,200 W through that cord; the rest of its capacity is reachable only through the 120 V receptacles on its own panel, or not at all. If your generator’s running rating is meaningfully above 7,200 W and you want all of it at the house, you need a 50 A connection.
The per-leg limit is what catches people out. Each hot leg carries at most 30 A, which is 3,600 W. If nearly everything you run is 120 V — refrigerator, lights, electronics, a space heater — and it all lands on one leg of the panel, that leg trips at 3,600 W while the generator sits at half load and the other leg does nothing. On a panel fed through an interlock or transfer switch, deliberately spread the circuits you energise across both legs. Some generators have a 120 V/240 V selector that combines both windings onto the 120 V outlets, which raises the single-leg limit and disables 240 V output entirely.
Then apply the continuous-load rule. NEC treats a load expected to run three hours or more as continuous and limits it to 80% of the circuit rating, which here is 24 A or 5,760 W at 240 V. An outage is continuous duty by definition. Planning around 5,700 W rather than 7,200 W also leaves headroom for motor starting surges and keeps the cord, plug, and inlet running cool, which matters more than it sounds when a cord is coiled in wet grass for three days.
Cords, adapters, and the mistakes that start fires
The cord must be 10 AWG four-conductor to carry the full 30 A. Buy 10/4 SOOW or SJOOW rubber cord with the W in the type code, because that is the marking that says it is rated for outdoor and wet use — this cord will lie in grass and puddles for days. At 30 A over 50 feet, 10 AWG loses about 3.7 V, roughly 1.5% at 240 V, which is entirely acceptable. At 100 feet that doubles to about 3%, still workable, and the point at which stepping up to 8 AWG starts to earn its cost.
Adapters are legitimate or lethal with very little in between. A listed L14-30P-to-two-5-20R splitter with correctly sized conductors is a real product and perfectly fine for running extension cords. A homemade version with 14 AWG lamp cord is a fire. And the specific device never to own or build is a double-male cord that plugs a generator into a dryer or range receptacle: it back-feeds the panel with no isolation whatsoever, energises the utility drop through the service transformer, and leaves exposed live pins in your hand while you do it.
On the house side, the L14-30 terminates in a flanged inlet — an L14-30P mounted in a weatherproof box on an exterior wall — wired in 10 AWG to either a transfer switch or a back-fed 30 A two-pole breaker behind an interlock. The whole safety argument is that the generator outlet, the cord, the inlet, the conductors, and the breaker are all rated 30 A. Putting a 50 A breaker ahead of a 30 A inlet, which happens when someone reuses an old range circuit, quietly removes the protection the cord depends on.
Frequently asked questions
How many watts can an L14-30 outlet handle?
7,200 watts at 240 V, which is 30 A × 240 V, split as a maximum of 3,600 W on each 120 V leg. For loads running three hours or more, the 80% continuous rule brings that down to 24 A, or 5,760 W. A generator rated above 7,200 W running cannot deliver its full output through a single L14-30 connection.
Is an L14-30 the same as a dryer outlet?
No. A dryer typically uses a 14-30R, which is a straight-blade 30 A 125/250 V receptacle. The L14-30R has the same voltage and current rating but locking, curved blades and is not physically compatible. Adapters between them exist and are the usual first step toward an illegal back-feed setup; if the goal is powering house circuits, the correct hardware is an inlet box plus a transfer switch or interlock.
What cord do I need for an L14-30 generator outlet?
10 AWG four-conductor cord — sold as 10/4 — with L14-30P ends and an outdoor-rated jacket type such as SOOW or SJOOW. Twenty-five feet is standard and fifty is common; beyond about a hundred feet, step up to 8 AWG to keep voltage drop under 3%. Never assemble one from a shorter cord and an adapter chain.
Can I plug an L14-30 generator into my house?
Only through a properly installed inlet box wired to a transfer switch or a listed panel interlock. That arrangement isolates the house from the utility so generator power cannot back-feed the grid. Plugging the generator into an existing receptacle with a double-ended cord does the opposite: it energises the service drop through the transformer at distribution voltage and can kill a line worker.
What is the difference between L14-30 and L14-20?
Only the current rating and, consequently, the blade geometry — the L14-20 is a 20 A version of the same four-wire 125/250 V configuration, good for 4,800 VA at 240 V rather than 7,200. The blades are shaped so the two cannot be mated, which is deliberate: a 20 A device must not accept a 30 A cord.