what are you welding? all thats all that counts is the duty cycle, not how much current your mains can handle. my 375 amper hardly gets used above 2nd seting out of about a dozen. thats down at summit like 100amps max i think.
a good 150 home welder jobbie will or should weld upto 6mm easily, only downside is they forever switch off on the thermal overload, that the only reason you might buy something well over what you need, then you can weld for longer, ours obviously never need to stop if running day and night. (as it is at the mo!)
I used to use a 500a water cooled BOC machine at around 300a for a 12 hour shift :roll: welding structural steel, after my 12 hours Tony would take his 12 hours :shock: It got 1 service in 3 years :roll:
Now I have a small Murex 253 that I use for general light fabrication out of 6 settings it rarely gets used on no.5 for channel or beam and 6mm op chequer :D and NEVER cuts out and I service it myself
If you buy a 100a welder and turn it up full it will last only a few minutes
I used to use a Clarke 140 stick welder on site for small jobs and could trip the thermal overload after 1+1/2 2.5mm rods :shock:
To get 100a for a decent period you need a 150a with cooling fan. The bigger the welder the better the mid range performance
I would also look for a 'euro torch' if within the budget as these are cheaper and easier to replace liners etc, and buy a decent brand :D
Steve