Horsepower vs Amps: Which Welder Spec Matters?

What horsepower means on a welder page

Horsepower shows up on a welder page in one clear place: an engine-driven welder. Those machines carry a small engine that turns a generator, and the maker lists the engine's horsepower so you know the size of the power plant. Miller, for example, sells engine-driven models such as the Bobcat and Trailblazer lines, and their pages name the engine along with the welding output.

On a shop welder that runs from a wall circuit, there is no engine, so no horsepower figure appears. The machine converts input current into welding current, and the maker states that result in amps. If a listing for a plug-in welder still mentions horsepower, treat it as marketing language, not as a specification that describes the arc.

The process a machine carries is the first word on a listing: MIG, TIG, stick, or multi-process. The maker states the output for that process in amps, and the input voltage the machine accepts. Horsepower has no part in that sentence for a plug-in machine.

Amperage is the output the maker states

The figure that describes what a welder can do is amperage output. Makers put a top output in amps at the top of a listing. Forney's 100 STx states 85 amps, and its 160 STx states 160 amps; YesWelder's ARC-205DS states 205 amps. These numbers are the headline of the listing, and they define the machine's range.

A welder's output is a window, not a single number. A listing shows a low and a high figure, and the machine works within that window. When you choose, you want a range that covers the work you plan to do, so read the stated range rather than a single peak figure. See what an amperage range means and how many amps a MIG machine needs.

The amp figure is stated for each process on a machine. A multi-process welder may list a MIG range, a TIG range, and a stick range separately. Those ranges are the details to compare, alongside the input voltage. The makers publish the ranges on their specification pages, and the buying guides on this site compare welders exactly that way.

Why horsepower does not describe the arc

Horsepower describes a mechanical engine's output. A welding arc is an electrical output. The two figures do not translate into each other, and a higher engine horsepower does not, by itself, tell you what the arc can deliver. The stated amperage at the process you plan to use is the figure to compare.

On a plug-in machine, the two useful input facts are the input voltage the machine accepts and the output amperage it states. Neither is a horsepower figure. If you are comparing a 120V machine with a 240V machine, the input voltage explains the ceiling; see 120V versus 240V input and output versus input power.

The title of a listing names the process and the top amp figure. A plug-in listing never states horsepower, because there is no engine. When a title does include the word horsepower, it is an engine-driven model, and that figure belongs to the engine, not to the welding output.

How a listing reads when both figures appear

On an engine-driven welder, you may see an engine rating in horsepower and a welding output in amps. Treat them as separate facts. The horsepower describes the engine, and the amperage describes the welding output. For the weld, read the amps; for the machine's engine, read the horsepower.

On a dual voltage or 120V machine, no horsepower appears; the stated output is amps at a given input voltage. Compare machines on their stated amperage output, not on any advertised phrase. The buying guides compare welders on stated details, and the dual voltage guide applies that to input voltage.

Engine-driven machines still list their welding output in amps, alongside the engine rating. The maker's page states the output range for each process, and that is the figure that tells you what the machine can weld. The engine horsepower is a separate fact about the power plant.

Questions to ask before you compare machines

When a listing states both an engine figure and a welding figure, ask which is which. The maker's page and manual name the output in amps for each process. The answers belong on the maker's page, not on a third party page.

• What is the stated output in amps for each process on the machine?
• What input voltage does the maker's manual name for each mode?
• Is the amperage range stated for the process you plan to use?
• For an engine-driven machine, what does the maker say the engine powers?
• Where is the specification sheet on the maker's site?
• Does the maker's page list the processes separately with their own amp ranges?

Reading the maker's specification sheet

Every maker publishes a specification sheet or manual for each machine. That sheet names the input voltage, the output range in amps, and the processes the machine supports. When a listing leaves out one of those details, the maker's page is the place to look. Everlast and Weldpro, for example, list their machines by series and point to specification pages for each model.

The American Welding Society describes welding as a profession with standards and certifications, which is why the maker's stated figures, rather than a marketplace phrase, are the source to compare. When the manual and the listing disagree, the manual is what the maker stands behind.

The specification sheet also states the machine's duty cycle in percentage terms, which describes how long the machine can run at a stated output before needing a cool-down period. Duty cycle is a separate figure from amperage, and it matters when you plan long work sessions. See duty cycle explained for what that term means.

What to pick for your situation

Questions

Does a higher horsepower figure mean a stronger weld?

No. Horsepower describes an engine, and on a plug-in welder it does not describe the arc. Compare the stated amperage output in amps.

Why do some welder listings show no horsepower?

Most shop and garage welders have no engine. They run on input voltage and state their output in amps, so no horsepower figure appears.

What does a listing's top amp figure tell me?

It states the highest output the maker lists for the machine. The useful reading is the full output range, not just the peak figure.

Where do I find the input voltage a machine needs?

In the maker's manual and specification sheet. The manual is the authority for the supply the machine needs; follow the maker's manual and local rules.

For an engine-driven welder, should I compare engine power first?

Compare the stated welding amperage first. Engine horsepower describes the engine, and the welding output is the figure that defines what the machine can do.

Can I compare horsepower figures across welders?

Only on engine-driven machines. For plug-in welders, no horsepower is stated, so compare amperage output and input voltage.