How to Choose the Best Generator to Suit Your Welding Machine

When you’re welding in an area without easy access to electricity, whether that be a farm fence, remote jobs, or off-grid locations, you will need a generator that can handle the job.

With so many generator options out there (diesel, petrol, inverter, standard), selecting the correct one for your needs can get confusing. You’ll need to take into consideration the fuel type, portability, power, and most importantly, if it can run your welder at the required output efficiently.

What is a generator?

A generator is a machine that turns mechanical energy (usually from fuel combustion) into electrical energy. This power can be used to run tools and machines like welders.

How does a generator work?

A generator burns fuel such as petrol, diesel, or gas to produce mechanical energy. That energy spins an alternator, which uses magnetic fields to generate electricity. Similar to the combustion engine of a car, in which explosions are created to move pistons, which power the vehicle. This electricity powers whatever is plugged into the generator, including welding equipment.

Why do you need a generator for welding?

Some of the common reasons for using a generator include:

No power access is available near your welding site
Working in sheds, or building without any wiring
Need a mobile setup for off-grid welding

If you don’t have reliable access to main power, a generator is your best option.

What size generator do you need for your welder?

The size of the generator depends on your welder’s input power requirements. To help, here’s a general guide:

Welder Amperage Output/Recommended Generator Size

Up to 140A / 8kVA

140A – 180A / 10kVA

180A – 200A / 11kVA

200A – 250A / 13kVA

350A+ / 20kVA

If your welder has a power Factor Correction (PFC), it may require a smaller generator than a machine without it.

Always check the welder’s data plate or spec sheet. Ask us at Gentronics for the recommended generator sizes for all welders.

Find Your Welder’s Wattage

To calculate how much power your generator needs to supply, you’ll need to convert the input amperage into watts.

Formula:

Volts x Amps = Watts

You will need two values

The input voltage (e.g, 240V)
The input amps

Don’t use the average current or input current; you need the maximum amperage.

Example:

240V x 25A = 6000W

Converting Watts to kVA

Once you’ve calculated your welders’ required wattage:

Formula:

Watts / 1000 = kVA

Then add 30% for surge/start-up current.

For Example:

6000W / 1000 = 6kVA

6kVA x 1.3 = 7.8kVA (roundup to 8kVA)

Clean power vs. Dirty power

Welders don’t like dirty power, especially inverter welders. If the generator’s output has harmonic distortion, it can

cause performance issues

Damage internal electronics

trip safety cut-outs

Harmonic distortion is measured in total harmonic distortion (THD). For inverter welders, aim for a generator with THD under 6%.

Transformer welders are more tolerant; however, inverter welders are more efficient – so clean power matters.

Standard Generators vs Inverter Generators

Standard Generator

Runs at constant RPM
Typically larger and louder
Suitable for transformer welders
May produce dirty power (higher THD)

Inverter Generator

Converts AC – DC – clean AC
Varies RPM based on power draw.
Compact, quieter, more fuel-efficient
Ideal for inverter welders and sensitive electronics

Other Considerations Before You Buy

1) Run Time

How long will you need continuous power? Some models run 8-10 hours; others may need refuelling sooner.

2) Extension leads

Avoid long cords if possible – voltage drop is a real issue. If necessary, use heavy-duty leads. Example guide:

Cable Size (mm squared) Max Length for 20A Input

2.5 mm 30m

4.0 mm 50m

3) Running Other Tools?

If you’re powering a grinder, drill, or lights alongside your welder, increase the generator size accordingly.

4) Altitude

At higher elevations, fuel engines lose power due to reduced oxygen. Account for that when welding in mountainous or remote areas.

Can a small generator run a welder?

It’s tempting to go smaller, but don’t.

A 5kVA generator might “start” your 180A welder; however, you would be underpowering it. You’ll likely face:

Overloads and shutdowns
Poor arc performance
Potential damage to both generators and the welder

Running multiple tools only adds to the strain. Always match or exceed your welder’s max power draw.

FAQS

What factors should I consider when choosing a generator for welding?

Input power requirements, generator type, THD, fuel type, and portability.

Can I use a standard generator with my welder?

Yes, but inverters are recommended for modern worlders.

What size generator is best for my welder?

Refer to your welder’s data plate or our sizing chart above.

Can I run other tools from the same generator?

Yes, but you’ll need more capacity. Add up all of the power requirements first.

Will a smaller generator damage my welder?

Yes, insufficient power can cause malfunctions or long-term damage.

If you’re unsure what generator best suits your welding set-up, contact us at Gentronics today. Our expert team can match you with the right gear based on your welder, workload, and environment.