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If you want start a Civil War in welding, you ask a group of welding experts which is better, an inverter or a transformer machine?

I get asked this question frequently and the short answer is, “it depends.”  The long answer is a lively debate surrounding pros, cons, and specific applications of the machines.

History of Transformers

Let’s begin the by understanding the history of transformers.  The first transformers were created as electricity became common in the late 1800s.  Soon it was discovered that transformers could be used in the arc welding process, which was in its infancy in the early 1900s.  It took a number of years to work through various electrical designs of machines to be able to control the arc.  This also brought about the need to create covered (or coated) arc welding electrodes commonly referred to as stick welding.

During WWI, welding went through a significant research and development phase with the construction of steel ships and early tanks.  Remember, before this time, steel joining was primarily done with rivets, forging, and gas welding.  Between the 1920s and 1930s, arc welding and transformer welding power supplies became common place.  As the power grid grew, arc welding grew with it.  By the end of WWII, the U.S. was experiencing a welding and manufacturing boom.  From the 1930s to 1980s almost all arc welding machines produced were transformer based which gave engineers and manufacturing more than 50 years to perfect the designs and create incredibly reliable arc welding machines.

History of Inverters

The next era started in the 1980s with the electronics explosion that coincided with personal computers.  As the electronics and software industry grew, engineers soon realized that software-controlled inverters could be used to weld; this opened up a new world of possibilities. The growing pains of inverters happened around the 1990s and many early inverter welding machines were plagued with reliability problems.  In the early 2000s, inverter welding machines were becoming popular because of their versatility and ability to control the arc.  The early inverter machines went through the normal engineering growing pains, which consisted of hotly contested topics around user interface, controls, heat dissipation, moisture concerns, and many other issues.  These issues are still at the core of the inverter adoption debate.

The Debate

This brings me to the reliability point that so many people like to debate.  For nearly a century, transformer machines have had extensive research and development to create reliable and rugged machines, while inverter machines have had only 30 years of similar attention. I still consider transformer machines to be more reliable than the best inverter machines but the gap has narrowed considerably over recent years.  Gone are the days of the 1990s where failures on inverters were the stuff of nightmares.


The next debatable point is versatility.  There was a point in time where transformer technology was mixing with inverter technology to create the ultimate welding machine but this path became overly complicated and expensive.  It soon became obvious to engineers that the advances in software and electronics were opening up a new challenge in the world of welding.  If you have any doubt about this, think about the first computers and cell phones versus what you have available today.  That same transition happened in the evolution of welding machines.  You can now buy inverter welding machines where you can adjust just about any electrical variable imaginable with software to create unmatched versatility.  Inverter machines are also much lighter and more portable than transformer machines.  I would have to give the edge to inverters regarding versatility.

Welds Produced

Considering we are discussing welding machines, we may want to get to the heart of welding and discuss the arc and the welds that are produced.  If I were the type of welder that only welds on mild steel all day, every day, I wouldn’t need to look past a transformer machine.  However, we live in a welding world that demands weld perfection in any position and on any material.  In this demanding world, inverters start to shine.  Since inverters can be programmed to do just about anything, we now see advanced pulse MIG performing as well as high skilled TIG.  There is a world opening up to us with software and advanced electronics that has really changed what a welding machine can do.  It even makes a mediocre welder like myself look pretty good at times.  I will give inverter machines a thumb up for weld quality and innovation but I still like to keep it simple for steel.


The last comment usually discussed is around price.  There was a time where inverter machines were incredibly expensive.  The high cost was derived from component costs, specialized manufacturing costs, and engineering costs.  Those costs have changed a lot over the last 15 years as inverters have entered the world of high volume electronics manufacturing.  I would now say that inverters are starting to become less expensive than transformer based machines, even though they are significantly more complex. 

When considering “cost” I think one should factor in a number of associated costs:

  • Initial purchase cost which is probably about even.
  • Power (electricity consumption) cost which is less with inverters.
  • Maintenance costs which after the warranty period is higher for inverters.
  • Downtime costs, which are debatable.
  • Quality of weld costs, which are also debatable.

All of this boils down to an application based discussion and whether transformer machines or inverter machines make more sense.  The following chart is a generalized opinion based on experience and lots of discussion.

Inverter is likely better: Transformer is likely better:
I want to Stick, MIG and TIG weld but only want one machine. I weld with one process every day all day.
I carry my welding machine to wherever I need to weld. I bring my welding work to my welding machine.
I weld on multiple types of base metal. I do the same job day in and day out.
I weld indoors in a controlled environment. I weld in dirty dusty environments.
I like touchscreens and lots of parameters to adjust. I like one or two simple knobs.
I like the welding machine to help me select the right settings. I know where my machine needs to be set.
I never know what power input I will have available when I’m on a job site. I have power to my welding area and I don’t move my machine.
I’m a tech geek. I’m old school.
I like tuning the ECU on my car. I appreciate old muscle cars.

I can confidently say that inverter welding machines have changed a lot in the last 15 years.  They continue to improve in both performance and cost but that doesn’t mean we need to dig a grave for transformer welding machines, as they still have an important place in our industry.


In the end, it comes down to a personal weighted decision based on many factors.  I know 20 years ago I stayed away from inverter machines and still love the arc characteristics of some of the high end transformer machines.  However, the arc controls on inverter machines allow me to dial in about any arc characteristic.  I also appreciate the light weight portability of an inverter machine.  I can honestly say I am no longer inverter resistant but gladly embrace inverter base welding machines just as much as transformer based machines.  At the end of the day, the choice is yours

Jason Mahugh, Director of Engineering, Forney Industries

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This post was originally published on March 29, 2017.