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How to Parallel Generators?

Generator Sets or Gensets offer a reliable way to provide backup power. Depending on the size and installation, we call them Portable Generators and Standby Generators. The most common use of a portable generator is to provide electricity in the event of a power outage or blackout. This usually happens during emergencies such as storms, hurricanes, floods, and other similar natural disasters. another common application of a generator is in worksites. Using extension cords with power tools is not at all recommended so many construction worksites use an on-field generator. Camping or RVs are also the main areas where we use a portable generator. We can charge the batteries in the RV or use the generator to directly provide power to different appliances.

In most of the above-mentioned applications, we use only one generator. What if you need more power from the generator? Can we use two or more generators, connect them in a proper way and extract more “wattage” from them? Yes. You can. We call the term Paralleling Generators or Parallel Operation of Generators. If you are looking for a similar solution then this guide is for you. Here, we are going to talk about all the basics of paralleling generators and also the procedure on how to parallel generators.


HOW TO PARALLEL GENERATORSInvesting in portable generators is a big deal. You have to consider a lot of variables such as total power requirements of the load, the power output of the generator, type of fuel, flexibility in terms of fuel (dual fuel generators), portability of the generator, and many others.

You bought a decent generator with all these things into consideration. And you were happy with the performance of the generator. But after a couple of years, your power requirements have increased and the current generator couldn’t deliver the necessary power.

This is not a unique situation as we have seen several generator owners who invested in slightly smaller generators that aren’t handling the additional power requirements well.

What to do in such situations? Should you ditch the present generator and purchase a larger, more powerful, and obviously expensive new generator? Or is there another alternative?

Turns out, there is a way you can continue using your current generator, and not spend a ridiculous amount on a larger generator. You have to purchase a new generator though, which is similar to the one you currently own.

The concept behind this is running two generators in parallel so that you get the combined power of the two but use it as a single power unit. If you are new to this concept, then continue reading as we will explore more on how to parallel generators.

What is the Parallel Operation of Generators? Or Paralleling of Generators?

When we configure two or more generators in such a way that they supply electricity to the same load (a common load), then the generators are said to be in parallel. There are several technical logistics behind the parallel operation of generators but essentially, we are connecting two (or more) generators to a common load and extracting the combined wattage from them.

For example, if you have two identical 2,000-Watt Generators and connected them in parallel. Then you can theoretically get 4,000 Watts out of them.

The Parallel Operation of Generators is not a new concept. It is quite common in commercial applications where instead of a single large unit, they use several smaller units in parallel. Here are some reasons why generators are run in parallel.

  • The first and obvious reason is the power requirements of the load. If the total power draw of the load exceeds the capacity of a single generator, then you can connect two generators in parallel and extract double the power.
  • When using more than one generator in parallel, the overall efficiency and reliability of the system will increase. It is often more than that of an individual generator.
  • Maintenance and servicing become easy if you have two (or) more generators in parallel. Even if you turn off one generator, there won’t be complete power loss as the other generator is still functioning.

Criteria for Paralleling Generators

If you are thinking of connecting two generators and running them in parallel, then it isn’t as simple as connecting them together and expecting them to work. There are certain requirements that you need to remember before going ahead.

First of all, not all generators support parallel operation. So, don’t blindly assume that a generator will be compatible connecting with other generators. There will be a clear mention on the generator (or in the official documentation) about the support for parallel operation.

Inverter Generators are one of the generator types that have a paralleling capability. Again, if your priority is to parallel generators, then check accurately from the manufacturer.

The speed of the generators must be a close match. Independently, they can operate at different engine speeds. But when working in parallel, we have to ensure that their engine speeds are in perfect sync.

Next, we have the electrical properties of both generators. The three important aspects of the generators here are frequency, voltage, and polarity (phase). For a successful parallel operation of generators, synchronization of generators with respect to these three specifications is very important.

In North America, the norm for single-phase AC Mains Supply is 120V and 60Hz. We expect the generators, be they portable or standby, also to produce electricity at similar voltage and frequency.

But the reality is not perfect and no two machines produce the same result. Even if you bought two identical generators (same manufacturer, same model, same batch, etc.), there will be a slight variation in their outputs.

But how much variation is acceptable if you want to parallel generators? For the output voltage, the difference must be less than five percent. The difference between the phase angles must not be greater than 5°.

Coming to the frequency, it is quite important that there should be no difference in the frequency of the output of the two generators. Most generators have engine governors to regulate or control the speed. These can be mechanical or electronic.

Regardless of the type, you have to make adjustments in the governors to synchronize the output voltage and frequency.

Another important aspect of governors is they will reduce the speed of the engine when we connect the generator to the load (or the load increases). This is also an important specification of both generators.

How to Parallel Generators?

Now that we have seen the basic requirements for paralleling generators, let us now see the procedure for how to parallel generators.

With Parallel Cable Kit

If you have two inverter generators that support parallel operation, then you are in luck. They are one of the easiest to operate in parallel. We highly recommend you purchase two generators from the same brand and preferably with the same ratings.

Next, the obvious step is to check if the inverter generator supports the parallel operation. There will be a marking on the front panel of the generator that says “Parallel Ready” or something similar.

Now, you have to purchase a Generator Parallel Kit, again from the same manufacturer as the generator. This is a special kit of connectors that helps in paralleling two generators.

It has two sets of Red, Black, and Green cables on either end. On the panel of the parallel connector, you have the output receptacles, whose output is a combination of both generators.

There will usually be two output ports on the parallel connector, one rated for 50A (with NEMA 14-50R Receptacle) and one rated for 30A (with NEMA L5-30R Receptacle).

Connecting the parallel kit is very easy. Start with one generator. First, connect the green ground connector. Then connect the red and black wires in that order. Repeat these steps with the other generator as well.

Now, you can start both generators and get double the output power from them (if they are identical).

The steps we mentioned here to connect a parallel kit may not be universal but you get the idea. Always refer to the user’s manual of the generators as well as the parallel kit.

For some models of generators, the sequence in which we turn on the generators is important. You can get accurate information regarding this in their respective user guide.

Manual Synchronization

You can manually synchronize two generators so that they can operate in parallel. Connect the first generator to a heavy resistive load such as an electric heater or electric stove. We call this generator the Running Generator.

Using gauges or meters, check the voltage and frequency of the generator and make sure that it is 120V and 60Hz.

Now open the breaker of the second generator and connect the generator to the same bus bar as the first generator. We call the second generator (the generator which we are synchronizing to the running generator) the Incoming Generator.

In order to synchronize the generators, you can connect two incandescent light bulbs across the poles of the circuit breaker of the incoming generator.

Depending on the frequency difference between the running generator and the incoming generator, the light will flicker. You can adjust the frequency of the second generator and as it approaches the frequency of the first generator, the flicker becomes slower.

If the frequency of both generators matches, the lamps will go completely dark and now you can close the circuit breaker of the incoming generator. Both the generators are now in sync and you can enjoy double the power output from them.

What are the Advantages of Running Parallel Generators?

Let us quickly see some advantages of paralleling generators.


The first and obvious advantage of connecting two generators in parallel is two get double the power, assuming you want to connect two identical generators. As the daily power requirements are increasing, one generator might not be able to provide adequate power for all your appliances.

By paralleling generators, you can double the power output and continue running large and power-hungry appliances.


The obvious doubt many have regarding paralleling generators is how economical is it. Is it a good idea to invest in another smaller generator (assuming you already have one)? Why not get a larger generator with a higher power rating?

You will save a lot by investing in a smaller generator (preferably identical to the one you own). The cost of a larger generator will be significantly more. Also, what are you going to do with the old small generator?

Selling it might be an option but again you have to do it at a significant loss. So, if you buy a second small generator, you can continue using the existing one, save a lot of money, and also get double the power.


Size is also another factor. Physically, even two small generators are small and weigh less than a single large generator. While residential users may or may not benefit from this, RV owners and people who use generators while camping will definitely benefit from the small size of generators (even if they are carrying two).


If you have two generators in parallel, you can continue operating the second generator even if there is a failure in the first generator. This type of operation is also useful while regular maintenance or servicing of generators.

While you repair (or service) one generator, the other generator will continue supplying power. Keep an eye on the load if you disconnect one generator as you are essentially halving the power rating.


The overall reliability of two generators running in parallel will be more when compared to using only one generator. Both generators will share the load so no one generator is under severe stress.


Continuing the reliability factor, the efficiency of running two generators in parallel is another major benefit. If you have a single large generator, its efficiency will be less than 30% when the load is small.

But with smaller generators, even with light loads, the percentage of the utilization of the generator’s capacity will be high. Hence, the overall efficiency will be more than 80%.


Generators are very useful devices, especially during natural disasters such as floods and storms. Also, in rural areas, where the reliability of the grid is questionable, to be frank, portable generators come in handy.

To save money, you bought a tiny portable generator after carefully calculating the power requirements of your residence, worksite, or RV. But as days go by, the power requirements increase with more powerful devices or an increase in the number of appliances.

You will reach a point where your current generator is running up to its brim and it couldn’t handle any additional load. The obvious solution to this problem might seem like giving up the existing generator and purchasing a new generator.

What if there is a way to continue using your current generator, make a small investment, and yet double the power ratings? We are talking about paralleling two generators.

In this guide, we saw the need for paralleling generators and how parallel operation of generators works. After that, we saw how to parallel generators and also some benefits of such paralleling.

We hope that this guide on the parallel operation of generators could help you understand the basics of running two generators in parallel. If you feel we missed something or want us to add anything, do let us know in the comments section below. It will not only help us but even other readers as well.

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