Although I have an extension cord, I found the easiest way was to add longer cables to the welder, so I didn't have to drag it outside everytime I wanted to use it. I think I added one or two sizes larger in size to the wire and went with 25 feet on the ground and 50 feet on the stinger side. The reason for the difference was I figured if I needed a longer ground, I could just add a piece of angle iron and tack it to whatever I couldn't reach with the shorter ground. You can just add connectors to the existing ones, but I wanted them to not get so warm while I was running the buzz box way past it's duty cycle...
Adding longer cables wasn't hard, but if making up an extension cord taxes your electrical knowledge, then have it done professionally.
David from jax