[Pumpiron01]

My friend gave me the small 90amp-AC 120V Harbor Freight flux core welder. I wanted to use it in the back of my truck off a generator. Looking around online people have been saying to find your wattage which is volts x amps. Find that then double it for a proper generator. So for a welder like mine it would need about 1800 watts so a 3600 watt generator. Does this sound right? Here are the welder's specs:

120 volts, 60 Hz, 20 amps, single phase input
Welding Output Range: 60-120 amps AC

[ldbtx]

20 amps * 120 volts = 2400 volt-amps. That's roughly equivalent to 2400 watts depending on the power factor, which we don't know. I'd use a minimum 5000 watt generator, just to make sure you're getting full output and not overheating the welder.

LDB

[Bill Beauregard]

But, most big box generators are 240 volt machines. At 120 volts you are using only one half of the winding in the generator. If the rating is legit, a 5,000 watt (5K) would do the job. the reality is most big box generators are badly overrated.

We should consider the usefulness of a 120 volt welder. Well powered, a 120 volt machine is severely limited as to what it can weld. Do you want to spend a bunch of money to power a welder that never could do the job? 120 volt machines are capable of welding steel 1/8", down to a point where it blows holes in the steel. Some will challenge the 1/8" figure, that isn't firm, they aren't as versatile as 240 volt machines which are more compatible with inexpensive generators.