What size generator to run 140 amp welder do I need?

The three most frequent considerations for both your welder and other power tools, when buying a power generator are practical usage, complete portability, and power backup.

Both pros and amateurs have experienced the frustration of an unstable power source. Finding out will some generator run a welder of yours or not is crucial for individuals whose work locations are outside the state’s permitted power supply boundaries.

We can all agree that we need a generator suitable for us with the proper equipment, tools, and a consistent power voltage source to complete any project successfully and to the fullest extent possible. When selecting one, we must carefully analyze all three options, conduct a thorough study, and deliberate.

Our work environment dictates the tools we use, but our comfort and efficiency also play a role in choosing the best equipment. The inverter welder we intend to power, however, is the lone factor in determining the ideal generator set.

If that’s the case, stay reading. If you’re reading this, you’re probably seeking to purchase a new generator for your welder or maybe you just want to learn more about welder gen sets.

Everything you should learn about selecting the properly sized generator for the inverter welder will be covered in this article.

What size generator do I need to run an inverter welder?

It’s a frequently asked question whether generator size matters for inverter welders. It depends. A modest generator should work just fine if you’re employing a small welder that doesn’t need a lot of electricity.

But you’ll need a bigger generator if you’re running a bigger welder that consumes more electricity.

When choosing what size generator to utilize for your welder, keep the following in mind.

Think about how many watts your welder needs. On the welding machine, most welders will have the information about power voltage stated.

Think about the generator’s input power in amps. It will also be listed in watts.

Consider how long it will take you to run the welding machine.

If you simply need to run the generator for a brief amount of time, a smaller generator will do. To manage the load, you will require a larger generator if you intend to run the welder for longer periods.

The main conclusion is that when it comes to generators, size does matter, but it all depends on your particular demands. To ensure that you purchase the right generator size for your welding needs, be sure to speak with a professional before making your final choice.

Choosing the size of a generator suitable for you to run a stick welder

When selecting the suitable size generator to power a welder, there are numerous aspects to take into account.

How many watts are needed to make a generator run a welder

The most crucial factor to take into account when purchasing a stick welder is the welder’s input power. A generator with at least 6,000 peak watts and more than 8,000 operating watts is what you should pick. The following advice will assist you in making the right decision.

You should examine the needed power before buying inverter welders.

The maximum amps specified on the welder’s data plate are often multiplied by the number of supplies and other electrical devices that are connected to the welder in order to determine the proper wattage for a welder’s complete operation.

Use a power generator that can deliver twice the welder’s maximum watts for the best results.

You need a generator that can produce enough watts to power a welder. A typical welder requires at least 3,000 watts of power.

Inverter welders with an inverter need 1.5 times as much power if you intend to use other tools, for example, a drill press.

For the generator to operate effectively, you should also make sure that it is safeguarded against overload, tripping, or fluctuation.

In addition

Additionally, bear in mind that for every 1,000 feet above sea level, welders might lose up to 3.5% of their output. A generator should be sized 25% to 30% larger than the welder’s wattage.

A smaller generator is therefore more prone to create larger input voltage spikes and frequency, which complicates the welding procedure.

How to determine the size

We don’t advise using the amperage output ratings to size a generator because welders are intricate and the manufacturers employ various designs and components to attain rated output levels (and also how they rate output varies).

No matter how many amps of input current welding machines can produce, the generator doesn’t care. The input voltage the welder uses to generate its welding amperage is what counts.

The generator output is typically measured in watts. Our fundamental formula is as follows:

Watts = Volts x Amps

This explains, for instance, that a generator with a 4800-watt rating that is powered by a 120-volt device can produce 40 amps of input current (4800 watts = 120 volts x 40 amps), and if it can also produce 240 volts, it can produce 20 amps of input current (4800 watts = 240 volts x 20 amps).

Add 800 to the output rating in kVa (kilovolt-ampere) to convert it to the input voltage. For instance, a 9 kVa generator multiplied by 800 produces 7200 watts.

For a generator, search for two output ratings. one for a continual, constant load sometimes referred to as the operational or running watts.

A small output spike that happens when a motor (or a welder) starts can also be handled by the majority of generators. This is known as the start-up or surge watt rating, which is typically 25–30% greater than the running amount.

The model name of most generators includes an input voltage. As the distinction between running and surge watts varies depending on the manufacturer, you should confirm this.

Knowing the maximum input voltage a welder will require is the first step in sizing a generator to supply that power. Then you’ll be aware of the power input voltage your welder must have to function at maximum efficiency.

A few factors that will aid in purchasing an efficient generator

There are several things to consider when buying a generator to power welding machines. The welder’s needed amperage is the most important consideration. Other elements consist of:

  • duty cycle of a welder
  • type of welding
  • power requirements for additional machinery used in conjunction with the welder

The size of the electrode, the welding rod, and the thickness of the metal ultimately determine the needed amperage. In contrast to a 3/32′′ electrode welding on thick metal, a 1/16′′ electrode welding on thin metal would demand less amperage.

The duty cycle is the length of time you can weld consistently without overheating the generator over 10 minutes. If your welder, for instance, has a 60% duty cycle, you can weld six times out of ten without endangering the generator.

The size of the generator is also influenced by the sort of welding being done.

For instance, arc welding demands more output power than stick welding, and if you’re doing a lot of starts and stops when welding, MIG or TIG welding needs even more power, which will also need more electricity from the generator.

The ideal course of action would be for you to take into account any other machinery that the generator would power while you are welding. This covers lamps, fans, and power devices. The total load on the generator will increase as a result of all this equipment.

Additional aspects to think about while purchasing a generator for a 140 amp welder

When buying a generator for a 140 amp welder, there are a few more things to bear in mind in addition to the ideal generator size and power. One is high altitude kits; if you operate the welder at a high altitude, you’ll need a generator with enough power output to make up for the thin air.

How long you need the generator to run before refueling is another consideration. Finally, if you plan to use the welder next to other people, you should think about the noise level. To avoid disturbing people or raising safety concerns, pick a quiet generator.

Transformers vs. Inverters

Transformers and inverter generators are the two primary generator types that power welding equipment. The following criteria should be taken into account when choosing the type of generator to utilize for your welding machine.

Weight and size

Compared to transformers, inverter generators are more portable since they are smaller and lighter.


Since they don’t waste as much energy as heat, inverters are more effective than transformers. To put it another way, they use less fuel.


Transformers are more affordable than inverters as generators and are simpler to repair if they malfunction.

Maximum Load

Additionally, because they are more durable, transformers can withstand being dropped or jostled. As a result, they can support heavier loads than inverters.

The variation in current flow quality

Power supply from the mains

There are no variations in the AC mains power supply. The power input voltage does not increase or peak abruptly. Welders and any power tools can be used safely with them. It ensures that any welder operates efficiently and provides protection from overloading and circuit breakdowns.

Power supply from the generators

There may be surges and spikes in the portable generators’ power supply. There is no question that this could affect welders. The performance and operation of the welder may be negatively impacted by the abrupt rise and fall in voltage. The likelihood of overloading and circuit breakdowns is rising.

How to pick the specific generator for a 140 AMP welder

There are a few factors you should think about when selecting the ideal generator for a 140 AMP welder.

enough welder’s input power to handle the load

First, make sure the generator has adequate power to manage the load. You must make sure that the welding generator can offer enough power because a 140 AMP welder can consume a lot of power.

Stability and constancy

Second, make sure the generator engine runs steadily and consistently to generate power. Make sure the generator power factor can supply the extremely reliable power source that many welders will need without an uninterrupted power supply.


Additionally, make sure the generator is robust and able to sustain frequent use. You need to guarantee that the generator can manage the demanding environments that many inverter welders are operated.

preferable Fuel type

Keep in mind the fuel type: is it gasoline or diesel? Which option will be most practical for you?

Petrol is typically less expensive if you have access to it, but diesel generators typically last longer and require less maintenance.

size of the generator

Next, consider the size of the generator that would be appropriate. It’s advisable to select a type of generator with a little greater wattage output to account for any additional devices or appliances you might want to power with it.

For instance, the maximum output needed for a 140 AMP welder is roughly 11,000 watts.

Other factors

Finally, take into account any other features you may value, such as an automated shut-off or an oil-level monitor. You may choose the best generator for your needs by keeping these considerations in mind.

Why could generator electricity be dangerous?

A sine wave is a pattern that the AC (mains) power supply uses. Power supplies with a perfectly clean sine wave, not a dirty power, are the safest when it comes to powering equipment with delicate electronics (such as computers and inverter machines), but in practice, this is almost unachievable.

Mains power rarely causes issues because it is (typically) quite near to perfect sine power.

While a portable generator’s power source is often the “dirty” power, the opposite is true. Even though the maximum output power may still show 240V on a basic measurement tool like a multimeter, the peaks, troughs, and cycle frequency will not be constant.

Voltage “surges” and “spikes,” which are voltage increases, can also be used to describe generator power (very sudden peaks of excessive voltage).

Voltage spikes and surges in a generator can happen for a variety of causes, such as the following.

Generator quality

When compared to ideal sine wave power, all portable generators often provide an erratic power supply. Total Harmonic Distortion, or THD, is a unit of measurement used to express how much the power of a sine wave varies from perfect sine wave power.

Generally speaking, a portable generator should have a THD rating of 6% or less.

The market has recently experienced a large influx of imports of inexpensive, subpar generators with unacceptable high THD ratings (above 6%).

However, because the voltage is more likely to vary and spike at an intolerably high level, these less expensive generators are not suited for running inverter-based devices.

Start-up and shutdown

When a generator is started and stopped, it is evident that the engine is not functioning properly and at a consistent speed, and as a result, the generator’s output is extremely likely to vary with engine speed.

Fuel supply interruption

Similar to starting and stopping, the engine will normally accelerate and decelerate spasmodically if the generator runs out of fuel or if there is a “hiccup” in the fuel delivery, resulting in power oscillations.

Generator size vs. loading

An undersized or overloaded generator will work extremely hard to attempt to maintain a suitable current supply.

The engine will then normally overrev until the governor brings it back to idle speed once the load has been removed (for example, when welding stops).

The voltage output will almost certainly grow as a result of this excessive generator revving, occasionally reaching a dangerous degree.

Further loads

If the generator size is insufficient, using other devices (such as a grinder, cut-off saw, etc.) on the same generator and at the same time as the welding equipment may overload it and result in power fluctuations.

Poor maintenance

A generator that has not been properly maintained would function like one that is of inferior quality.


When using the generator for welding, its size is important. After reading this post, perhaps you won’t wonder what size generator you need for a welder.

You are aware that the generator has various sizes. Additionally, not all sizes are suitable for all kinds of welding. Therefore, when selecting a generator for the welding activity, you must take the various welding kinds into account.

Read also: The Best Generator For Food Truck: Top 7 Current Generators For Your Food Truck With Generator Features

Frequently Asked Questions (FAQs):

What size generator do I need to run a 140 MIG welder?

Depending on the type of welder you are looking to run will determine the size generator that you will need.
Most smaller mig and portable 120-volt welders can be run off a 5000-watt to 7000-watt generator.
All larger arc welders will require a much larger generator upwards or 50 amp output.

What size generator do I need to run a 150 amp welder?

Many welders with 140-150 amp of input current may draw less than 30 amps when they first turn on, but some require almost 40 amps.
To be safe, double the voltage for the maximum watts by the I1max (max amps) rating. A 140-150 amp input current welder will require between 3600 and 4800 watts to operate at full capacity.

How thick can I weld with 140 amp welder?

A 140-amp welder is capable of completing a variety of welding tasks.
This welder has some limitations due to various variables. It has a greater range of possible jobs if the machine is AC/DC competent.
With a 140 amp of DC electrode positive, 1/2″ (12 mm) of steel can be welded reasonably well, and a 5/32″ (4 mm) welding rod may be burned quite easily.

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