Portable Generator Receptacles: All You Need to Know

Power outlets, interchangeably also receptacles or sockets, can be hard to navigate. Life would be much easier if there was just a single universal electrical outlet but unfortunately, that’s not the case.

Yet, what if there was a single source with all the info you’ll ever need to guide you through this tedious topic?

This article covers everything you need to know about power outlets as a portable generator owner (in Northern America).

We will introduce how outlets are classified and then follow up with a list of each outlet that matters to you. To top it off, we will introduce some key safety features which you should keep in mind when operating a portable generator.

Motivation. Why isn’t There Just a Single Outlet?

Let’s get things straight. Why should this matter to you?

If you take a look at any of the many generators in our database and scroll down through their data sheet, you’ll find that they are equipped with multiple receptacles. As you may suspect, these receptacles are used to draw power from the generator and deliver it to the appliances which you wish to power.

Annoyingly, not all generators have the same number or even kind of receptacles. Thus, to avoid major inconveniences, a generator owner must know which and how many outlets he’ll need before making a purchase.

Likewise, if you already own a portable generator, you should know which outlets it’s equipped with and which you may be missing. It is also helpful to know what they’re for, how they are rated, their cross-compatibility with different plugs and how they may be adapted.

Westingouse WGen12000DF outlets

Some units, such as the Westinghouse WGen12000DF, can have quite a fair number of outlets

Having more than one outlet on a generator is not a cosmetic choice. Indeed, different designs of outlets have a practical purpose – to most effectively deliver power to the appliances which they are intended for, which must be reflected in their wiring schemes.

Thankfully, the choice of AC receptacles and plugs is narrowed down by NEMA standards (opens in a new tab), which ensure that every company doesn’t make their own outlets and leave the consequences of such mess up to you. (Note that NEMA is a trade association, not a governmental body. However, regulatory standards adopt their classification.) This doesn’t apply to DC outlets, which we’ll also cover later in this article.

NEMA Classification. How are Receptacles Named?

You have most likely already encountered at some point in your life plugs and receptacles with different shapes. In Norther America, these differently shaped connectors have a name, usually something like NEMA 5-15R. This is their NEMA classification.

Standardized NEMA outlets are differentiated both for practical and technical purposes – so that they deliver effectively different types of current and so that they are or aren’t compatible when necessary, to avoid both their user’s frustration and potential accidents. That’s how we arrive at numerous types of receptacles and plugs with different shapes and ratings.

Quite understandably, common folk may be intimidated by codes such as “NEMA 5-15R” at first sight, especially if they find out that just the first of these numbers ranges from 1 to 30 and each of them defines a unique shape of connectors. So, how do you sort through them?

Sorting Out Connector Names

Connectors are designed and classified with respect to voltage, amperage, phasing, grounding, and number of wires/prongs.

You are reading, of course, a portable generator blog, not an electrical engineering textbook. Thus, we won’t be going through each of these terms in much detail.

All of the aforementioned parameters are reflected in the NEMA electrical code, which has 4 variables/identifiers, as indicated in the chart below.

nema nomenclature chart

In summary:

  1. The 1st identifier indicates whether the outlet is equipped with a twist-lock mechanism, by the letter L.
  2. The 2nd identifier indicates the voltage, but also other information, such as whether the connection is grounded, the number of its poles, wires and phase of the current.
  3. The 3rd identifier indicates the numerical value of the current (amps) that the outlet is rated for.
  4. The 4th identifier indicates whether the “connector” is a plug P or receptacle R.

Notice that upon breaking the nomenclature down, all these descriptors are pretty straight forward, with the exception of the second, which is loaded with information. Though this number is tricky, fear not! You are likely to only encounter NEMA 1, 5, 6, 10 and 14 plugs and receptacles in your daily lives, and NEMA 5 and 14 receptacles if considering just those relevant to portable generators.

AC Receptacles and Portable Generators

The following is an overview of AC receptacles which are employed in portable generators. Please note that this is far from a complete list (opens in a new tab) of the existing and commonly used household and industrial connectors.

NEMA 5 Connectors (120 V)

NEMA 5 plugs and receptacles are three-wire (hot-neutral-ground) grounding devices rated for maximum voltage of 125 V, though they are commonly referred to as 120 V plugs/sockets, since that is their usual nominal voltage. NEMA 1 plugs are upwards compatible with NEMA 5 receptacles, however, the opposite is not true for NEMA 5 plugs. Both NEMA 1 and NEMA 5 connectors have the same shape and rating, but unlike NEMA 5, NEMA 1 connectors are not grounded (consult manufacturer of respective appliances before you plug any of these in).

Portable generators may come with the following NEMA 5 receptacles:

NEMA 5-20R Outlets

duplex 5-20r gfci, 5-20p plug, 1-15p plug

From the left, NEMA 5-20R GFCI duplex, 5-20P plug, and 1-15P plug (note that NEMA 1 and NEMA 5 analogs differ only by a grounding pin).

NEMA 5-20R is the common household outlet for 120 V/20 A. It can provide power of up to 2400 W.

The standard NEMA 5-20R outlet can accept both NEMA 5-15P and 5-20P plugs, though you may rarely find 5-20R receptacles with modified slots, which are limited only to NEMA 5-20P plugs.

Same applies to upwards compatible NEMA 1 plugs. NEMA 5-20R outlets usually come in duplexes, which always share a single circuit breaker and may also have a shared GFCI protection.

NEMA L5-30R and L5-20R Outlets

NEMA L5-30R, L5-30P, L5-20R, L5-20P

From the left, NEMA L5-30R outlet, L5-30P plug, L5-20R outlet, and L5-20P plug

NEMA L5-20R and L5-30R are twist-lock equipped 120 V/20A and 120 V/30A outlets, respectively. Following the same order, they can provide power of up to 2400 W and 3600 W. Note that twist-lock equipped plugs and receptacles are NOT compatible with their non-twist lock counterparts without a suitable adapter.

NEMA L5-30R receptacles are often found in docks and campsites, where they are used to connect vessels (boats, RVs, etc.) to shore power. Although some RVs are equipped exclusively with NEMA TT-30R outlets, NEMA L5-30R can still be used to power them with a suitable adapter.

Both NEMA L5-30R and L5-20R are also utilized in extension cords, e.g., for lawn mowers or hedge trimmers, where they protect from accidental disconnection, moisture, etc.

NEMA TT-30R Outlets

TT-30R, TT-30P

NEMA TT-30R outlet (left) and TT-30P plug (right)

NEMA TT-30R is a modified NEMA 5-30R receptacle, widely employed in RVs and trailers, for 120 V/30A. It can provide power of up to 3600 W.

Generators equipped with these receptacles are considered RV Ready.

As mentioned above, NEMA L5-30, 5-30 and TT-30 connectors can be all interfaced using a suitable adapter (please consult relevant manufacturers’ information before doing so).

NEMA 14 Connectors (120/240V)

NEMA 14 plugs and receptacles are four-wire (hot-hot-neutral-ground) grounding devices rated for a maximum voltage of 250 V, though they are commonly referred to as 120/240V plugs/sockets, since that is their usual nominal voltage. Two different voltages (indicated by the slash) can be provided by these connectors thanks to their four-wire design, which features two hot connections. In addition, NEMA 14 connectors support a three-phase power supply of 120/208V, though it is not commonly employed and is irrelevant to the topic of portable generators.

Note that NEMA 10 connectors are upwards compatible (opens in a new tab) with NEMA 14 connectors, analogously to NEMA 1 and NEMA 5 connectors. However, we strongly discourage you from doing so as this practice requires additional grounding measures.

Portable generators may come with the following NEMA 14 receptacles:

NEMA 14-50R Outlets

14-50R, 14-50P

NEMA 14-50R outlet (left) and 14-50P plug (right)

NEMA 14-50R is a 120/240V, 50A receptacle. It can provide power of up to 12,000 W.

The outlet is quite commonly utilized to power demanding appliances, such as electric cooking ranges.

NEMA 14-50 connectors are also used to power large RVs which are beyond the scope of NEMA TT-30 connectors.

NEMA L14-30R and L14-20R Outlets

L14-30R, L14-30P, L14-20R, L14-20P

From the left, NEMA L14-30R outlet, L14-30P plug, L14-20R outlet, and L14-20P plug

NEMA L14-30R and L14-20R are twist-lock equipped 120/240V, 30A and 120/240V, 20A receptacles, respectively. In the same order, they can provide power of up to 7200 W or 4800 W.

NEMA L14-30 connectors are commonly used to power household appliances which require 240 V and to hook up home backup generators to transfer switches. On the other hand, NEMA L14-20 connectors are rarely encountered. Note that both connectors can be interfaced with their non-twist-locked counterparts by an appropriate adapter.

NEMA SS2-50R Outlets

SS2-50R, SS2-50P

NEMA SS2-50R outlet (left) and SS2-50P plug (right)

NEMA SS2-50R is a twist-lock equipped 120/240V, 50A receptacle. It is somewhat rare in portable generators, though apparently quite widely utilized to hook up boats to shore power.

Given their specs, NEMA SS2-50 connectors should be adaptable to NEMA 14-50 connectors, though we recommend checking with the relevant manufacturers’ info before attempting to do so.

The Honda EB10000 is one of the rare portable generators that feature this outlet.

DC Receptacles and Portable Generators

While NEMA has at first sight complex, but consistent and reliable standards, they apply only to AC outlets. DC outlets, on the other hand, vary quite wildly (opens in a new tab). Even established DC connectors vary significantly in voltages and amps, depending on where they are applied. Thus, always check the parameters of both your power source and appliances before you hook them up!

12V DC Receptacles

3 types of 12V DC receptacles

3 different types of 12 V DC receptacles frequently found on portable generators

12V DC connectors come in various shapes and sizes. The ones which are commonly employed in portable generators are some of the many flat or cylindrical connectors, banana connectors, and sometimes even 12 V automobile auxiliary power outlets. Such connectors can be used to power and charge small devices, batteries and electronics (including sensitive devices such as phones or laptops).

Note that the design of DC connectors is quite inconsistent and even connectors which are at first sight identical may utilize different pin design, length and diameter. Moreover, 12 V DC connectors may vary significantly in supplied current. Refer to user manuals for exact specs of the connector to ensure that your devices are compatible.

USB Ports (5 V)

dual 5V USB ports

A fair number of units feature dual 5 V USB ports

Over the past few years, portable generators have thankfully adopted the practice of including USB ports in their control panels. Given that most DC-powered electronics are USB compatible, this solves most issues with DC outlet compatibility.

However, even USB ports may differ significantly in the amps they provide. Most devices tolerate 1.0A current. However, it is common to encounter USB outlets which supply a current of 2.1A and higher, which is not necessarily compatible (opens in a new tab) with some small devices with old circuitry, e.g., vape pens, wireless headphones, etc. This may result in your devices refusing to charge, or charging at ridiculously low speeds.

Given the current trends in USB charger technology, the same may soon apply to the supplied voltage, as even 5 V USB chargers are being replaced by higher-voltage devices.

Other Outlets

Lastly, our list wouldn’t be complete without including outlets which we labeled as “other”. These outlets are completely unstandardized and vary by manufacturer or sometimes even from model to model.

Parallel Ports

parallel ports

Parallel ports are only found on inverter generators

Inverter generators quite often feature so-called parallel ports. These are, as their name suggests, used to hook up two or more generators in parallel, to increase the power supplied to a circuit.

Generators with parallel ports are labeled as “parallel capable”. However, a parallel kit which includes all the parts required for a parallel setup is often not included in the package and thus must be purchased separately (you can find this information in our generator datasheets).

Proprietary Outlets

ST Switch outlet

The ST Switch outlet is a feature of some Westinghouse generators

Some generators include additional proprietary ports for various accessories, which are often designed uniquely for a model or a series.

The best examples of these proprietary outlets are outlets of welding generators for welding equipment or outlets of home backup generators for proprietary transfer switches.

A Few More Things to Consider

The last section of this overview focuses on some features of electrical outlets which are relevant to running a portable generator.

Outlet Protection (GFCI and others)

Outlets may be protected by various protection mechanisms, which are intended to increase the safety of the user and their equipment. These include:

GFCI Receptacles

Duplex 5-20R GFCI outlet

GFCI outlets have Test/Reset buttons

A GFCI (opens in a new tab) (ground fault circuit interrupter) receptacle disconnects the power supply when a new ground connection appears in a circuit, which is detected by an imbalance between incoming and outgoing current. GFCI receptacles are usually designed in a duplex and feature a test and reset button.

Upon tripping, the power supply is cut off and the reset button slides out. The power is restored by pushing the button back in.

The test button interrupts the grounding and is intended to test the functionality of the GFCI circuit. This test should be frequently conducted as part of your maintenance routine.

Tamper-Resistant Receptacles

Tamper-resistant receptacles (opens in a new tab) are designed to reduce shock hazard upon manually tampering with them by preventing direct contact with the wires from the outside. This has been the mandated design of all household receptacles since 2008 by the National Electrical Code and is often employed in portable generators. They can be identified by the letters “TR”.

Weather-Resistant Receptacles

Weather-resistant receptacles are designed to resist UV light, cold and moisture. They have been mandated since 2008 by the National Electrical Code for all outdoor, damp and wet locations and although they are hard to identify going by user manuals, they should be installed in most portable generators as well. They can be identified by the letters “WR”.

On top of that, manufacturers may improve the durability of their generator’s receptacles by introducing covered outlets. Covers are usually made from durable, light-weight and water resistant rubber materials.

Circuit Breakers

Circuit breakers (opens in a new tab) save both equipment and lives by tripping the circuit upon detecting an excess of current which may be caused by either an overload or a short-circuit. A distinction is made between the terms “surge” and “excess” of power, which is the main difference between circuit breakers and GFCI. This is important, as a GFCI unit is likely to trip when drawing starting watts, whereas a circuit breaker is not (or rather is less likely). Vice versa, a GFCI is more likely to save you if a blow dryer falls into your bathtub, whereas a circuit breaker is not.

Portable generator manufacturers may use circuit breakers to limit the output of their units. e.g., if a 6000 W (starting watts) generator is equipped with a NEMA L14-30R receptacle, which is rated for up to 7200 W, the supply will be limited by changing the 30A circuit breaker into a 25A one. The user should be aware of this when using this outlet.

Last thing to consider is that it is common to have individual circuit breakers for each receptacle, with the exception of duplexes. As a result, a NEMA 5-20R duplex is limited by a single 20A circuit breaker, which means that each receptacle’s current will be limited by the shared 20A limit.

Conclusion

In summary, we have learned why portable generators are equipped with multiple different outlets, how they’re classified and how they’re different. We have learned that AC outlets use NEMA nomenclature and have broken down their naming pattern into comprehensive segments. The commonly employed receptacles in portable generators are NEMA 5 and NEMA 14, each of which has different capabilities and uses.

We have also introduced commonly encountered DC outlets and to top it all off, we have talked a bit about the protections designed into outlets and the impact of circuit breakers on the current drawn from them.

Paul

Paul

Manager & Editor of generatorbible.com. Early retired from the OPE industry, living in South Carolina. He now mostly spends his time traveling and taking care of his wife and grand-children.

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