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Generator Receptacles - The Complete Guide

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Life would be much less complicated if there were just one standard electrical socket in use everywhere in the world. This article will teach you all you need to know about power outlets for your portable generator.

If you own or are thinking about buying a portable generator, it would be beneficial to understand how outlets are classified, and this article will do just that. Last but not least, this piece will go over some basic safety measures you should follow whenever you use a portable generator.

Why is there not just one plug?

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If you take a close look at some of the generators on the market, you'll see that they come with many plugs. As you might expect, these outlets are used to connect the generator to the devices you wish to power.

It's unfortunate that not all generators have the same quantity or quality of plugs. Consequently, before buying, a generator owner should count the number and type of outlets he will need to ensure safety. You should also know what outlets your portable generator has and what you might be lacking if you currently own one.

Knowing their intended usage, ratings, compatibility with different plugs, and modifiability is also helpful. There is nothing worse than buying a new generator and it is not fit for purpose with how you intend to use it. 

Having numerous outlets on a generator is useful, and not just for convenience. In truth, different outlet designs have a practical purpose, reflected in their respective wiring schemes: to supply power to the specified equipment in the most efficient manner possible.

As luck would have it, you can usually find ways to adapt these ports on your portable generator so that they work with a wider variety of devices. However, you need to be aware that doing so may affect the warranty. 

How to identify receptacles

Connectors are designed and sorted in accordance with the voltage, amperage, phasing, grounding, and number of wires/prongs.

The presence or absence of a twist-lock mechanism on the outlet can be deduced from the presence of the letter L in the first identifier.

The second label shows the voltage and other information, such as the number of wires, the number of poles, the phase of the current, and whether or not the connection is grounded.

The third symbol denotes the maximum amps that can be plugged into the socket.

With the fourth identifier, you can tell if the "connection" is a plug P or a receptacle R.

When the terminology is stripped away, you can see that all of these traits are easily understood, with the exception of maybe the second but I wouldn't worry about it too much. In normal life, you'll usually run into NEMA 1, 5, 6, 10, and 14 plugs and receptacles, or maybe just NEMA 5 and 14 receptacles if you're using a old portable generator.

Common generator receptacles

Let's take a look at the most common power outlets for generators today. Most generators advertise their 20 and 30 Amp ratings and use a combination of conventional duplex connectors plus at least one locking plug (usually an L5, L10, or L14). To accommodate recreational vehicles and trailer needs, some manufacturers offer TT-30 plugs.

If you need to replace your home's electrical cords or plugs/receptacles, be sure to get ones with matching amperage and types. Since the prong configurations of a 20 Amp receptacle and a 30 Amp plug are not identical for any given NEMA L type, just something to be aware of.

Single phase appliances, like family units and common household appliances, require a NEMA 1 for 2 prongs, a NEMA 5, 6, or 10 for 3 prongs, and a NEMA 14 for 4 prongs when operating in the 120V/125V and 240V/250V zones.

NEMA 5-20R power outlets

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NEMA 5-20R is the standard home outlet for 120 V/20 A. It has the capacity to supply up to 2400 W of power.

The standard NEMA 5-20R outlet accepts both NEMA 5-15P and 5-20P plugs; however, you could occasionally encounter NEMA 5-20R receptacles with altered slots that only permit NEMA 5-20P plugs.

An identical statement applies to upgradeable NEMA 1 plugs. Duplex NEMA 5-20R outlets often share a single circuit breaker and may share ground fault circuit interrupter (GFCI) protection.

NEMA TT-30R power outlets

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The NEMA TT-30R, a 120 V/30 A variant of the NEMA 5-30R receptacle, is commonly found in recreational vehicles and trailers. It can produce up to 3600 W of power.

Only generators with these plugs are considered RV ready.

NEMA L5-30, 5-30, and TT-30 connections can all be interfaced with the right adaptor, this is an important receptacle for off-grid camping and tailgating so be aware of that.

NEMA L14-30R and L14-20R power outlets

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NEMA L14-30R and L14-20R refer to twist-lock receptacles rated for 120/240V at 30 amps and 20 amps, respectively. When utilized sequentially, they have the potential to generate 7200 W or 4800 W, respectively.

NEMA L14-30 connectors are commonly used to connect home backup generators to transfer switches and to provide electricity to 240 V home appliances. Conversely, NEMA L14-20 connectors are rarely seen. Bear in mind that an appropriate adaptor can be used to join each connector to its non-twist-locked counterpart. 

DC power outlets

Most portable generators include one of three common types of 12 V DC plugs.

There is a wide range of sizes and shapes available for 12V DC connectors. Portable generators typically use a variety of different types of connectors, including flat or cylindrical plugs, banana plugs, and even 12 V vehicle auxiliary power outlets.

Batteries, electronics, and other small devices can all be charged and powered with these connectors, but make sure the THD is suitable for sensitive equipment like laptops. 

Keep in mind that there is a vast range of DC connector types; even seemingly identical connectors could have pin designs that vary in length and diameter. Furthermore, 12 V DC connectors' supplied current may fluctuate widely.

The user manuals should have the exact specs of the connectors, so that you can be confident your gadgets will work together.

USB power outlets

Thankfully, USB ports have become standard on portable generators' control panels in recent years. Since the most majority of USB-compatible devices run on DC power, this solves the vast majority of DC outlet compatibility issues.

The amps provided by USB ports, however, may vary widely. A current of 1.0A is safe for most devices. Some small devices, such as vape pens, wireless headphones, etc., may not be able to handle the higher currents that USB outlets of 2.1A and above often provide.

This could cause your devices to cease charging altogether or to charge at absurdly sluggish speeds.

USC ports are becoming more common now, and in places like Europe could totally replace USB for good. 

How to hook up a generator to your home

We know what receptacles a generator has, but you will need to know how to use it to make the receptacles usable to you.

It is a good idea to invest in a home backup generator in case of a prolonged power outage for the sake of your family's safety. There are a plethora of options for generators of varying capacities and price points.

No matter the model, there are two basic options for connecting a portable generator to a house.

  • By using a range of power cords
  • Using a transfer switch to link your generator to the home

Alternative, more involved methods include solar power and battery backup systems. For the sake of clarity, I'll focus on the most common scenarios.

Before we start wiring your portable generator into your home, please remember these two things:

Exhaust fumes from a generator should be kept outside at all times to protect users from carbon monoxide and always consult the generator's manual for operating instructions.

Use of transfer systems

The safest way to connect a generator to your home is using a transfer system. A transfer system allows you to switch between the power supplied by the energy grid and that supplied by your own generator.

When you install a transfer system in your home, the circuits in your walls will become active, allowing you to use any appliance that is hardwired into your home. Everything in your home, including the lights, ceiling fans, air conditioners, etc., would work as long as you have a powerful enough generator.

There is a risk of electrocution when working with electricity, and a transfer switch must be installed with a complete understanding of how it functions. You might decide to do the installation yourself or to get professional help. If you want to be safe, we recommend having an electrician install and test the switch.

After a transfer switch has been installed, connecting your generator is as simple as plugging it in and flipping a switch. The transfer switch can be used to activate an automatic generator start when power is lost in the home.

Use of a power cord

Some generators include a four-pronged 20/30-amp socket, whereas others have simply the more common three-pronged 20A 120V AC outlet. Using a 4-prong outlet with a gen-cord is ideal since it is safer to do so and distributes the power from your generator more evenly.


Most gen-cords have a four-prong plug that you use to connect to your generator. The opposite end typically has several plugs with a 3-prong configuration. Plug in the generator and run the extension cord inside through an open door or window. Then, you may plug in your appliances and electronics using extension cords.

Extension cords

Most generators have a 120V AC outlet (wall outlet) that can be used to connect an extension cord. There, you may plug in your various electronic devices and home appliances.

In order to power your entire home, you will need more than just an extension cord connected to your generator. This method works great for running a few electronics, but if you need to run your entire home, you'll need a transfer switch.

In addition, 14-gauge extension cords with more than three prongs are required; 12-gauge cords are preferred.

Under no circumstances should you plug your generator into an indoor outlet. This is what is meant by the term "backfeeding." You, a utility worker, or your neighbors could be seriously hurt or perhaps killed if you backfeed the electricity.

Using a GFCI transfer switch with a GFCI generator

GFCI (ground fault circuit interrupter) outlets are required by the NEC (National Electrical Code) to be installed on dual-voltage generators (those that produce 120 and 240 volts). 

To safely connect a generator with GFCI outlets, a transfer switch designed for this purpose must be used. This switch, also known as a three-pole switch or a GFCI-compatible switch, is required by the NEC.

By flipping this switch, you can isolate the generator's 120-volt circuits from the utility's 120-volt circuits and disconnect the neutral, which is the third leg of the utility's circuit. 

If you connect a standard 2-pole transfer switch to a generator that has GFCI outlets, the GFCI outlets will trip (which does not isolate the neutral).

By flipping this switch, you have violated electrical safety regulations and diminished the output of the generator. It's too bad, because you forked over extra cash for GFCI safeguards. A 3-pole switch or a 2-pole transfer switch can be used for non-GFCI generators.


The standard range of generators uses duplex 5-20 plugs and receptacles, plus an L14 in either 20 or 30 amps. These generators typically have a power output of less than 10 kilowatts. If you need a multifunctional plug for your RV, look no further than the TT-30.

About Tom Bell

Hey, I’m Tom, the owner of Generator Reviews! I built this website to help you get the very most out of your generator and select the correct one for your personal circumstances. This site contains reviews of virtually every generator, detailed buying guides, as well as maintenance advice to help you keep yours in tip-top shape!


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