What size breaker does a welder need? Read it from the manual, not the badge
A welder's output amps do not tell you its breaker. Where the manufacturer publishes input amps, breaker and wire size, and what to take to your electrician.
You are about to buy a welder and the listing says 200 amps. Your panel says 100 amps. Those two numbers have almost nothing to do with each other, and neither one tells you the breaker.
The breaker a welder needs comes from its input current, which the manufacturer publishes in the manual. It does not come from the output amps on the badge. Output amps are what flows through the arc at around 20 volts. Input amps are what the machine pulls from your wall at 120 or 240 volts. A breaker (the switch in your panel that cuts power when a circuit draws too much) only sees the input side.
Where the number is published
Look in three places, in this order.
- The “Electrical Service Guide” or “Input power” section of the owner’s manual. Miller, Hobart and Lincoln manuals print a table per input voltage: input amps at rated output, the maximum recommended fuse or breaker, the minimum conductor size (wire gauge, written AWG, where a smaller number is a thicker wire) and the longest allowed run.
- The nameplate on the machine. Machines built to IEC 60974-1 show I1max (the most the machine draws at maximum rated output) and I1eff (the effective draw once duty cycle is counted).
- The spec sheet. Usually input amps only.
If none of the three gives a breaker size, the answer for that model is “Not published”. We do not back-calculate one from output amps, and we suggest you do not either. Our welder comparison table prints the manufacturer’s figures with the model number and the date checked.
A worked example from published specs
| Machine and input | Rated output | Input amps at rated output | Circuit the manufacturer requires |
|---|---|---|---|
| Hobart Handler 140, 115 V | 90 A at 20 percent | 20 A | 20 A individual branch circuit |
| Hobart Handler 210 MVP, 115 V | 90 A at 20 percent | 20 A | 20 A individual branch circuit |
| Hobart Handler 210 MVP, 230 V | 150 A at 30 percent | 24 A | See the manual’s Electrical Service Guide |
Sources, both checked 2026-09-19: the Handler 140 spec sheet, stock number 500 500 (copy hosted by Northern Tool), and the Handler 210 MVP owner’s manual OM-260 274, section 5-8 (ManualsLib).
Read the first row again. At a rated output of only 90 amps, the Handler 140 already draws 20 amps from the wall, and its spec sheet lists 2.5 kilowatts of input. A 120 volt, 15 amp outlet carries about 1,800 watts. A 20 amp circuit carries about 2,400. That is the electrical ceiling on every 120 volt welder, whatever the badge says. It is also why the manual asks for an individual branch circuit, meaning one that feeds this outlet and nothing else.
The 230 volt row shows the other side. The same family of machine delivers 150 amps of output while drawing 24 amps, because doubling the voltage roughly halves the current for the same power. More on that in 110v vs 220v welders.
Why welder circuits have their own rules
A welder does not pull its full current continuously. Duty cycle caps how long it runs in any ten minutes. The US National Electrical Code recognizes this with a dedicated article for welders, Article 630, which sets conductor and breaker rules from the nameplate currents and the duty cycle. Hobart’s manual cites it directly (sections 630.11 and 630.12).
The practical result is that a welder circuit is sized differently from a general-purpose circuit, and the combinations that are acceptable depend on the machine, the run length and your local code. That is a licensed electrician’s decision. We do not publish wiring instructions.
What to take to the electrician
- The model number and a copy of the manual page with the electrical service table.
- I1max and I1eff from the nameplate, if shown.
- The input voltage you plan to use, and whether the machine is a dual voltage welder.
- Where the machine will sit, so the run length can be measured.
- Your panel’s main breaker rating and how many spaces are free. A photo of the open panel door helps.
A 100 amp panel is not automatically too small, and a 200 amp panel is not automatically fine. It depends on what else the panel serves, which we cover in can my panel handle a welder. That is a load calculation, and it is part of what you are paying the electrician for.
If the numbers are missing
Some import machines publish output amps and a duty cycle and nothing about input. Ask the seller for the manual before ordering. If the manual has no input current and no breaker recommendation, you cannot plan the circuit, and your electrician cannot either. We treat a missing input spec as a finding, and it costs a machine points in our scoring.
Frequently asked questions
What size breaker do I need for a 120 volt welder?
Read the manual for your model. As one published example, Hobart requires a 20 ampere individual branch circuit, protected by time-delay fuses or a circuit breaker, for the Handler 140 and for the Handler 210 MVP on 115 volt input. An individual branch circuit serves only that one outlet. Many garage outlets are 15 amp and shared with lights or a door opener.
Do I need a 50 amp breaker for a 240 volt welder?
Not necessarily. 50 amp is a common welder receptacle rating, but the machine's requirement comes from its input amps. The Hobart Handler 210 MVP draws 24 amps at rated output on 230 volts. The breaker and wire your installation needs are for a licensed electrician to decide from the manual and your local code.
What do I1max and I1eff mean on a welder nameplate?
They are the two input currents defined by IEC 60974-1. I1max is the most the machine draws from the wall at its maximum rated output. I1eff is the effective input current once duty cycle is taken into account, so it is lower. In the US, National Electrical Code Article 630 uses these values for welder circuits. Your electrician will ask for both.
Why is welder wiring different from a normal circuit?
Because a welder does not draw its full current continuously. Duty cycle limits how long it runs, so the National Electrical Code has a dedicated article for welders (Article 630) with its own rules for conductors and overcurrent protection. Applying it is a licensed electrician's job. We publish the manufacturer's numbers so you can have that conversation.
Can I run a welder on a 15 amp outlet?
Only if the manufacturer says so for that model, and usually at reduced output. A 120 volt, 15 amp circuit carries about 1,800 watts in total. The Handler 140 spec sheet lists 20 amps of input at its 90 amp rated output, which is more than a 15 amp circuit supplies.