Portable Generator Receptacles

It can be difficult to understand electrical terminology and all the different portable generator receptacles’ nomenclatures.

Do you know what a NEMA connector is? How about a GFCI outlet? If not, don’t worry; you’re not alone.

So We’ve created this guide to help clear up some of your confusion as a portable generator owner. In it, we’ll explain electrical terms like “NEMA classification” and “GFCI outlets” and how these outlets are classified, and we’ll also outline the features of common outlet types like AC receptacles and DC receptacles.

Why no single universal outlet exists?

The question that most people frequently ask is, “why no single universal electrical outlet exists” to power household appliances. The simple answer to this query is all the power-demanding appliances connected to the generator’s receptacles are different in terms of power rating, voltage grade, number of wires, or cores in the cable.

Every plug and cord has a current and voltage rating by its manufacturer. Using an underrated cable or plug to suit the receptacle may pose a safety hazard. If connected to a lower current rated cable, high current drawing equipment can cause a fire. Similarly, a 125 V rated cable should not be used on 120 / 240V equipment.

The manufacturers provide an inlet and a detachable power cord with an appropriate plug on the equipment to avoid complications. To sum up, different designs of power outlets on your portable generators are intended to deliver power to your equipment safely and reliably, depending on their wiring schemes.

Before purchasing a new portable generator, thoroughly review the appliances you want to power and come up with your requirements for cords, plugs, and receptacles to hook up. Then go through the generator datasheets to select a matching generator. Of course, the number of outlets on any generator matches their power output and increases with their running watts.

If you already own a portable generator, you should be aware of its rating, compatibility with different types of plugs, what additional receptacles you wish your machine to have, and if it is feasible to select an appropriate adapter to suit your needs.

Names of Standardized NEMA Outlets

If you are in North America, chances are that you are already familiar with NEMA, which stands for “National Electrical Manufacturers Association.” Formed in 1926, it is involved in publishing the standards for electrical products in North America. While doing so, it ensures interoperability between the products and safety. This list includes portable generator plugs and receptacles.

NEMA Electrical Code for Plugs & Receptacles

All types of plugs and receptacles are assigned a unique “name” or “code” that distinguishes them from the other power outlets in terms of

  1. Type – Locking, non-locking straight blade, etc.
  2. Voltage Rating, number of poles, wires, and phases. The voltage rating of receptacles can vary from 125 V to 600V.
  3. The current Rating can vary from 15 to 60 A.
  4. To convey whether the device is a plug or a receptacle.

The nomenclature of this coding is NEMA XY AB, where the variables or identifiers X, Y, A, and B are assigned different values for differently shaped connectors based on the abovementioned four considerations. The possible values for the identifiers are (the identifiers can take many values depending on the application, but we will restrict ourselves to the values that are common on the portable generator receptacles):

  1. “X” Identifier – If X identifier has been assigned a value “B,” this indicates that it is a locking device. It is a straight blade type device with no locking ability if nothing is assigned.
  2. “Y” Identifier – The “Y” identifier can be assigned two values, “5” or “14”. NEMA 5 indicates that the device is a three-wire grounding device suitable for a maximum voltage rating of 125V. NEMA 14 are four-wire grounding devices suitable for 250V.
  3. “A” Identifier – Indicates the current rating. Common values are 15A, 20A, 30A, and 50A.
  4. “B” Identifier – It can be assigned two values, “P” or “R” for plug and receptacle, respectively.

The identifier “Y” carries much more information than the number of wires, grounding, and voltage. As we move further in our article, we will get the hang of this.

AC Receptacles On Portable Generators

Let us briefly introduce you to all the types of AC outlets used by portable generator manufacturers on their machines.

NEMA – 5 Outlets

As briefly introduced in the previous section, NEMA – 5 plugs and receptacles are three-wire grounding devices with hot-neutral-ground pins rated 125V. They are the grounded versions of NEMA – 1 devices, as all other things like shape and rating are the same for both of these devices except for the additional ground pin. The grounding pin is larger than the power blades to ensure the device gets grounded before receiving power.

NEMA – 1 devices are upward compatible with NEMA – 5, but not vice versa.

NEMA 5 – Non-Twist Lock Type Receptacles

NEMA 5-15R and 5-20R are North America’s most common non-twist lock type electrical receptacles. However, most portable generators use 5-20R as 120V/20A outlet to feed 2.4 kW of power supply unity power factor.

Portable Generator Receptacles NEMA 5-15

As against 5-15P, the 5-20P plug has its neutral blade notated by 90° and shifted to ensure that the inner edge of its blade is at least half an inch away from the hot blade. So effectively, NEMA 5-20R has a T-shaped neutral hole to accommodate 5-15P and 5-20P plugs.

These outlets are commonly used in duplex configuration, where they may share a single circuit breaker and even the ground fault circuit interrupter (GFCI) protection.

NEMA TT-30R outlets

The term “TT” stands for a travel trailer in this outlet’s name. As is evident from its name, it is most commonly used in RVs and trailers. It is also known as RV 30. The outlet is rated for a supplied voltage of 120V and 30A current. Sometimes, people confuse this outlet with NEMA 10, rated for 240V.

Both hot and neutral blades are perpendicular to each other and at an angle of 45° from the vertical. The portable generators equipped with TT-30R outlets are considered RV-ready. Adapters are available to interface TT-30R, NEMA L5-30R, and NEMA 5-30R outlets with each other.

NEMA 5 – Twist Lock TYPE Receptacles

The locking-type connectors are preferred for commercial and industrial applications where vibration or accidental pulling of the cord may disengage the nonlocking types. They are denoted by the letter “L” before the usual code. These connectors have curved blades in the plug that are pushed into the receptacle and twisted to latch to the receptacle.

Another important feature of their design is the incompatibility between different voltages and current ratings, making it impossible, even accidentally, to connect them. Of course, if the pull on the cable is too hard, the cable itself will come out instead of the plug. In this category, L5-20R and L5-30R outlets find frequent use on your portable generators.

As in 5-20R, these receptacles L5-20R and L5-30R are suitable for 120V/20A and 120V/30A, respectively, corresponding to 2.4 kW and 3.6 kW power at unity power factor.

They are commonly used to feed power to the docked boats and on the RV end of the cord to connect to the shore power. At home, they are used in extension cords for gardening equipment.

NEMA 14 Outlets

NEMA 14 plugs and receptacles are four-wire grounding devices with two hot connections, one neutral, and one ground connection. This configuration allows them to effectively deliver power at 120 V or 240 V. This outlet can support a three-phase supply of 120/208V, though not commonly used. Anyway, your portable generators produce only single-phase power.

It is rated for a 250 V power supply with current ratings ranging from 15 A to 60 A. These outlets are similar and backward compatible with NEMA 10 devices, the difference being only in the grounding connection.

Out of various NEMA 14 outlets, only 14-30 and 14-50 are commonly used for electric clothes dryers and electric cooking ranges, respectively. It is possible to use them for charging electric vehicles. Let us look at NEMA 14 outlets in detail.

NEMA 14 – Non-Twist Lock type OUTLETS

On portable generators from NEMA 14 series, you will find only NEMA 14-50 outlets find frequent use in RV parks, where they shore power for large RVs. They were previously used to connect mobile homes to utility power. They are now getting used for Tesla mobile connectors for vehicle charging applications.

NEMA 14 – Twist Lock Type Connectors

NEMA L14-20R and NEMA L14-30R are the three-pole and ground connectors for three-pole four-wire applications requiring twist-lock connectors. Like their nonlocking counterparts, they provide 120 V from hot to neutral and 240 V between two hot terminals for appliances requiring 240 V.

30A connector finds applications in racks of large audio amplifiers and household backup generators when you require to hook them with the transfer switches.

NEMA SS2 – 50R is a twist Lock type “SS” series 50A connector. SS stands for “ship to shore” hence these connectors are primarily used for marine to shore applications. SS2 are three poles with ground connectors rated for 125V/250V, while the SS1 series are two-pole with ground outlets rated 125V.

DC Connectors

As the name implies, DC connectors, also known as DC outlets, are the electrical connectors that supply DC power. They are not governed by NEMA-like standards for AC outlets. The DC connectors are classified as ultra-low voltage (below 120 V) and low voltage (120 V to 1500 V).

While not standardized, the DC power connectors are available in three common configurations – jack, plug, and receptacles. A DC jack is mounted on an appliance, PCB, or chassis and receives supply for most DC-powered electronics. Plugs and receptacles are connected to power cords and feed power to them.

The DC receptacles frequently found on most portable generators are cylindrical, banana, flat connectors, or automobile auxiliary power outlets. The cylindrical connectors are also known as barrel connectors.

The DC barrel plug has two connectors, the center pin and the outer sleeve. In most cases, the central pin carries power, and the outer sleeve is the ground connection. Reverse configuration is also acceptable. Check this aspect before making any connection, as inverted polarity may cause damage to the circuit.

It is important to note the inner pin and outer sleeve diameters and the insertion lengths. This will allow a proper mating connection between the plugs and receptacles. Sometimes a third conductor is available to detect the insertion of the plug by forming a switch when the outer sleeve.

The main function of these outlets is to power small devices or charge them. In addition, they can charge 12V batteries in many portable generators.

USB Outlets

Everybody uses USB these days for data transfer and powering small devices requiring 5 V or lower voltage. Most portable generator brands include USB ports on their control panels.

The new Type C is bidirectional and reversible. USB connectors are governed by three standards – the physical connector, power delivery, and data transmission.

USB PD 3.1 standard has 24 pins – 16 for data, 4 for power, and 4 for ground. It can deliver 240W of maximum power at a maximum voltage of 28/36/48 V and a maximum current of 5A.

Parallel Ports

If you want to connect two or more generators in parallel to increase the power output, you may use the parallel ports available on the parallel-capable portable inverter generators.

You may use either a specially designed parallel cable supplied by the generator manufacturer or a separate parallel kit that acts as a central outlet for the purpose.

Proprietary Outlets

Some generator brands include specific proprietary outlets

  • If the generator is designed for a specific application. For example, welding generators may include them for connecting the welding equipment.
  • The generator manufacturer may also be manufacturing proprietary transfer switches for home backup generators and would like to include a proprietary outlet to connect to their Gensets.

Other Outlets

There are other outlets on the control panel of the portable generator

  • GFCI receptacles with outlet protection from a ground fault,
  • Tamper-resistant industrial connectors,
  • weather-resistant outlets,
  • circuit breakers, etc.

We have covered them in our separate article on GFCI outlets.


That’s a lot of information, but I hope you now understand the different types of electrical outlets and connectors better. If there are any specific questions that you still have, please let me know in the comments section, and I will do my best to answer them. And don’t forget to share this post with your friends and family – they may find it helpful too!

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