Hooking a Mig welder Up to a Generator

Last Updated on July 4, 2022

It is crucial to understand the difference between a welding generator and an ordinary portable generator. A welding generator primarily works with a constant load, but conventional generator is not:

  1. You start the generator and turn on the welder, but there is no load yet;
  2. As soon as the electrode touches the metal, an electric arc arises and the load jumps to the maximum
  3. As soon as you remove the electrode and the arc disappears, the load drops again and the engine idles.

It is essential to note that welding machines typically have large starting currents. For this reason, you cannot use them with just any type of generator. To succeed in using a welding generator effectively, you must get a portable generator that commands a large starting current.

You should note that a standard asynchronous gas generator produces wave surges. Due to this situation, the engine efficiency is usually compromised and, therefore, drops significantly. The service life of any equipment that you connect to it also tends to reduce. For a good run and optimal performance with a welder, you always require a stable voltage as a prerequisite.

Stable Voltage

The perfect alternative would be to use inverter power generators. Unfortunately, they are often too expensive when compared with the cost of buying a conventional generator. In ideal situations, inverter generators are designed for use with high precision equipment. They are suitable for measuring devices that require a stable voltage.

Whenever you decide to buy a generator, it is wise to select a model that commands power rated at about 25-50% more than that produced by your welding machine. It is easy to explain this: The regular operation of the generator at its maximum capacity can bring it down very quickly. Moreover, this situation will not allow the generator to use the welding machine at its full potential.

How to Calculate Generator Power for Welding

It might be that, for some reasons, you do not have information about the power capacity of your welding inverter. How should you go about it? It is easy to calculate this using a simple formula. Here is the formula as outlined below:

Maximum current strength * arc voltage / Efficiency of the welding inverter = Maximum Power.

 You only need to know the value of the maximum current. This is true because the other two components are almost always constant (the arc voltage is 25v, and the inverter efficiency is 0.85).

Let us consider one example: If your welding machine has a maximum current of 180 Amps, then its power is approximately 180A * 25V / 0.85 = 5294 W. This means that the generator value is 5294 W + 25% margin = 6617.5 W. If we translate this into kW, it comes to 6.6 kW. In such a case, the best choice for welding will be the Honda EU7000is or a similar generator of equivalent power.

Reducing Amperage

You can easily use a generator for inverter welding. Regardless, the power of the chosen generator should be less than that of the inverter. In such cases, you should use it with some caution. This means you must reduce the amperage to the recommended value.

What would happen if, for instance, you decided to purchase a 4 kW generator model? To find out, we can use the formula that is employed in determining power capacity. The only difference is that we would do this in the reverse order. Consider the formula used below:

Power * Efficiency / arc voltage = Current or 4000 * 0.85 / 25 = 136 A.

You can actually weld using your 4 kW generator and an inverter. You can do this without any perceptible loss of quality. Indeed, you can muster a current strength of up to 130A in this manner.

Choice of Power on the Electrodes Diameter

If you have to use electrodes of a larger diameter, then the choice of power should be of a higher current strength. This is because there is a relationship between the load network and the diameter of the electrodes. Let’s look at the table of the diameter of electrodes, as shown here:

Electrode DiameterMinimum generator power
2/25"  2.0 mm2.5 kW
0.12"  3.00 mm3.5 kW
5/32'' 4.0 mm4.5 kW
5.0 mm5.5 kW

To analyze this data, consider an example: If your inverter welding is fed from 4.5 kW, then the most significant electrodes with which you can weld a metal are 4 mm. If you insert a 5 mm electrode, the 4.5 kW quantity of power will not be enough to melt the high-quality metal. In such a case, the resultant seam will either be poor quality or not welded at all. For these reasons, autonomous power must be chosen primarily by considering the inverter’s maximum potential.

Remember this cardinal principle: Not all welding machines can work from the generator and vice versa. With this in mind, before buying, check with the seller whether the preferred welding model can work from the power plant. One significant point is that the manufacturer always indicates this in the product manual.

Welder + Portable Generator vs Welding generator

The welding generator combines the design of both the gas generator and the welding machine. The typical power plant is designed in such a way as to enable welding activity. This generator, therefore, usually has a longer life.

The welding generator offers the following notable advantages:

  • Protection against short circuits.
  • You can work in remote locations, away from the central power supply. This can be the outskirts of the city, far away fields, or far-flung roads.
  • Enables a more compact design than if the welding were connected separately.
  • Costs less than a diesel generator of similar power.


  • This electric generator can only be used for welding.
  • It uses gasoline, which generates higher fuel consumption than diesel.
  • It cannot be powered from the central network.
  • It has a shorter lifespan.

Overall, the most significant limitation of the welding generator is that it cannot be used as a backup power source. This generator is intended only for welding. The welding generator is, however, the best option if you are professionally engaged in repair work or continually travels to places where there is no access to electricity.

You do not have to connect and adjust anything; start the engine, and adjust the current to the diameter of the electrode. Happily, this machine has fewer wires and is, therefore, easier to manage.

How Do You Connect the Welding machine to a Portable Generator?

To connect the welder to the generator, you can buy a twist-lock plug to fit the generator. Cut off the welder plug and wire the cable to the new plug. In case you wish to use the welder with permanent power and a matching outlet, go ahead and make an adapter.

Buy a male twist-lock connector to fit the generator. You also need two or three feet of 10/3 flexible rubber cable, type SOW or SJOW. Finally, get a matching receptacle for the welder plug and make a short extension cord or adapter. With this done, you are good to go!


The welding generator is your best bet if you often travel to far-flung areas of the countryside where the power grid is inaccessible. Are you a repairman who is perennially committed to jobs that require quick welding? The welding generator will do you proud. For such workers, it is certainly useful to learn how to connect an welding inverter to a portable generator. Hopefully, this article will help you.

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