Will A Portable Generator Run A Welder?

  • By: Umer.A
  • Date: October 10, 2021
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It is better to complete your welding project on the field instead of in the shop. But for that, you will need a portable generator. And the good thing is, modern welders and generators have become quite powerful and compact too. Therefore, welding at remote sites has become much easier.

But you need to know what type and size of a portable generator will cut it for you. Too big will not be easy to carry. If it is too small, it cannot power your welder.

So, in this guide, we will find out, can you use a portable generator to run a welder?

How Can You Size a Generator for Welding?

Determining generator wattage

Generator outputs are mentioned in Watts that is a product of voltage and amperage. So, for example, a generator rated for 4800W will be able to provide you 40 Amp current at 120V. Or it can also provide you with 20 Amp of current at 240V.

You can convert the output rated for kilovolt-ampere (kVa) into wattage by multiplying the result with 800. For instance, if you have a generator rating of 8 kVa, multiplying it with 800 will give you 6400W.

You have two ratings to look for in a generator. One is the running watts while the other is the surge watts. Running watts are associated with a constant load, while surge watts are associated with an output spike when you start the generator.

The surge wattage rating is always around 25% to 30% higher than the running wattage. So, now the only thing that you need to know is how much wattage your welder will draw at max capacity.

Determining welder wattage

Determining the total wattage of your welder is not as simple. This is because these welders don’t have their wattages listed in their specs. But there are a few manufacturers that will provide you with minimum generator size recommendations for their welders.

However, even a welder doesn’t come with its wattage in the specs. Instead, you can calculate it using its amperage and voltage number. These numbers are given in the owner’s manual and the data plate on your welder.

It’s best to go for the welders that have their voltage given in “U1”. This is what they use to measure the voltage and amperage of their welder. The number written against “I1max” will tell you about the surge or inrush wattage required for the welder.

Adjust your generator before Welding

There are a few more things to consider before finalizing a generator for your welder.

  • Consider high altitude operations because thinning air at high altitudes means less power. If you are going to do some welding on higher altitudes, you need to go for a welder with an altitude adjustment setting. You can also buy these altitude adjustment kits for your generator.
  • Plus, you need to consider any accessory equipment that you will be using during your work. For example, you might have to use fans, lights, or compressors during welding. Therefore, you need to add their wattage to the equation as well.

Traditional vs. Inverter Welders

The internal power of welders can be categorized into two subtypes. And they both handle the incoming current in entirely different ways to create power output.

Conventional welders

These are the transformer-style welders that are of aluminum and copper and are pretty heavy. They can change AC input into low voltage or high amperage DC output for welding. These are not sensitive to dirty power and are extremely reliable. These welders can work pretty well with any generator.

Inverter welders

With technological advancement, it has become possible to create more efficient welding output with even smaller transformers. So, these inverter welders tend to weigh more than half of the traditional welders.

These inverter welders can achieve a stable output as they come with capacitors that can store high voltages in them. But you can run these welders on dirty power. So, they need to run only on clean energy that doesn’t come with any fluctuations whatsoever.

Many generators can cause voltage spikes and distortions, and this is what “dirty power” is. It is measured in THD or total harmonic distortion. This dirty power tends to manage sensitive electronics or reduce service life.

Conventional vs. Inverter Generators for Welders

There are two types of generators that you can use to power your welders. These are conventional generators and inverter generators.

Conventional generators

These generators have AC alternators that are driven by a motor. They can produce power in just one step, and that is to spin the alternator at around 3600 RPM and create 120V and 60Hz frequencies.

If there is any variation in this speed, there will be fluctuations in the frequency and voltage, and it will result in harmonic distortion, which ultimately means dirty power.

To tackle this, you will need a transformed-style welder that can easily handle these fluctuations. However, as the power doesn’t need clean standards, you can’t run your inverter-style welders on these traditional generators.

Inverter generators

Inverter generators have the same technology to create a stable output also works for generators to produce clean energy.

These generators can generate high-frequency alternating current with an alternator that is driven by an engine. After that, the alternate current converts into direct current, and it is inverted into a stable and lower alternate current supply.

As these units start with higher energy, they have more control over the final output. So, the harmonic distortion is always going to be under 5%. This is great for both conventional as well as inverter welders along with various other sensitive electronics.

Can A Portable Generator Run a Welder?

A portable generator will only run on a welder if it’s the right size and capacity. For example, if your welder output is up to 160 Amp, the minimum generator size should be 7 kVa, and the maximum size is over 8 kVa.

However, if the maximum welder output is between 180 Amp to 200 Amp, then the minimum size should be 8 kVa, and the max size should be over 10 kVa. And if your welder’s maximum output is 250 Amp, the minimum recommended size is 13 kVa, and the max recommended size is over 15 kVa.

In other words, according to these ratings, a portable generator can run a welder pretty conveniently. But you have to make sure you seriously consider the overall quality of the portable generator apart from its size.

Important features to consider when buying a portable generator for a welder

First of all, you need to determine the output of your welder and then look for the right-sized generator with a suitable capacity. You also need to consider the type of welder that you own. After that, you should determine what capacity and size of generator you need and the type of generator you should go for.

Can I run a welder with a 3000W portable generator?

A 3000W portable generator will produce a 25 Amp current at 120V. However, many 120V welders can draw up much more amperes right at the start (surge voltage). Therefore, a smaller welder with 90 Amp or 100 Amp output should work pretty well with a 3000W portable generator.

Is a 5000W portable generator good enough to run a welder?

Yes, a 5000W portable generator will be enough for your 120V welder that can draw energy under 40 Amps right at startup. This includes more welders that can draw up to 160 Amps as well. However, most 240V machines require more than 5000W to function at their total capacity.

For a 140 Amp welder, what generator size should I opt?

Many welders come with a rating of 140-Amp output, and they can draw less than 30 Amps right at the startup. However, some do need around 40 Amps as well.

To be safe, you need to go for the maxim ampere rating and multiply it with voltage to get the maximum wattage. So, for a 140 Amp welder function at full capacity, you will need a 3600W to 4800W generator. And in this wattage range, portable generators are easily available now.


You might either have a welder for which you are looking for a portable generator or own a generator and look for a welder that you can use with it. In either case, you need to look for the right wattage capacity for both units.

Thanks to technological advancement, you can buy a portable generator that can run a welder these days. But before you finalize your decisions, make sure you check the wattage ratings of both units so you don’t end up wasting your time and money buying the wrong options.