Generator for Welder: Power Requirements

What a welder needs from a generator

A welder is a high-draw tool. When you read a generator listing, the two numbers that matter most are the starting watts and the running watts. The starting watts cover the brief surge when the welder's motor or transformer first energizes, and the running watts cover the steady draw while you are welding. The welder's manual states its input wattage and the plug type it uses; that is the figure to match against the generator's stated output.

This site compares generators on stated details only. The catalogue does not publish measured output, so the way to compare is to read the running watts and the outlet configuration on each listing and on the maker's page. If a listing does not state a figure, the detail is simply not there to compare.

Generator output versus welder output

Generator output is rated in watts, and welder output is rated in amperes at a given voltage, for example 140 amps at 20 volts. These are two different measures. The generator's job is to supply the electrical input the welder needs; the welder's job is to convert that input into the arc. You cannot read a welder's amperage rating and assume it equals the generator's wattage. The welder's input requirement, in watts, is what you compare with the generator's running watts.

A listing may say a generator is 'welder ready' or 'for welding use.' That phrase means the generator has the outlet and the wattage capacity the seller believes suits a welder. It does not replace reading the welder's manual. The manual tells you the exact input watts and the plug configuration, and the generator listing tells you the outlet types and the wattage figures. Match those two sets of stated details.

Outlet types for welders

Many welders need a 240-volt outlet, often a NEMA 6-50 or 14-50 style plug, though smaller units may use a 120-volt outlet. The generator listing states which outlets are built in, and the maker's page usually lists the receptacle types. If the welder's plug does not match an outlet on the generator, an adapter may exist, but the decision about whether an adapter is appropriate belongs to the welder's maker and a qualified electrician.

For a 240-volt welder, look for a generator that states a 240-volt outlet in its specifications. The generator outlet types guide explains how to read outlet names on a listing. The 120V vs 240V for welder article covers the difference in plain terms.

Wattage groups and welder size

Welders range from small hobby units to heavy industrial machines, and the generator wattage group you need follows the welder's input. A small 120-volt welder may run on a generator in the 3,000 to 5,000 watt range, while a larger 240-volt unit may need a generator in the 5,001 to 9,000 watt range. The listing's first watt figure is often the starting figure, so read the second figure for running watts.

The running watts vs starting watts article explains the two figures. For a welder, the starting surge can be significant, so the generator's starting watts must cover that brief peak. The running watts must cover the welder's steady draw while you are welding. If the welder's manual does not state input watts, contact the welder's maker.

Fuel and generator type for welding

The fuel type on a generator listing, gasoline, dual fuel, or tri fuel, does not change the wattage math. What matters is that the generator's stated output meets the welder's input. Dual fuel and tri fuel listings add the option of running on propane or natural gas, which may matter for fuel availability on a job site, but the wattage figures are what you compare.

Inverter generators and conventional open-frame generators both list wattage figures. For a welder, the key is the wattage and the outlet, not the inverter technology. The inverter vs conventional generator article explains the difference in listing terms. The portable generator guide covers open-frame options, and the inverter generator guide covers inverter options.

A note on carbon monoxide

Generators produce carbon monoxide, an odorless, colorless gas that can be deadly. The CPSC states that one generator produces as much CO as hundreds of cars and that it can kill you in minutes. Never run a generator indoors, in a garage, basement, crawlspace, or shed, and keep it outside well away from windows, doors, and vents. Always have a working CO alarm in the house. Follow the maker's manual and read the CPSC and CDC carbon monoxide pages in the sources for this article.

What to pick for your situation

Questions

Can I use a generator's starting watts to size for a welder?

Starting watts cover the brief surge when the welder starts. The generator's starting watts must be at least as high as the welder's starting draw, and the running watts must cover the steady draw while welding. Read both figures on the listing.

What outlet do I need for a welder?

Many welders use a 240-volt outlet, such as a NEMA 6-50 or 14-50, but smaller units may use 120 volts. The welder's manual states the plug type, and the generator listing states the outlets. Match them.

Is a generator's wattage the same as a welder's amperage?

No. Generator output is in watts; welder output is in amperes at a given voltage. The welder's input requirement, in watts, is what you compare with the generator's running watts.

Do I need an inverter generator for a welder?

The inverter technology does not change the wattage or outlet requirements. What matters is that the generator's stated output and outlets match the welder's input needs. Inverter and conventional generators both list wattage figures.

Where can I find the wattage my welder needs?

The welder's manual or nameplate states the input watts and the plug type. If it is not there, contact the welder's maker. The generator listing states running and starting watts; compare those figures.