That depends on the diameter of the studs to be welded as well as the required welding current. In general, you need to make sure that the generator has enough power. This ensures good-quality and reliable welds.
You can use this diagram as a guide. Use the welding current as a reference and select a generator that supplies power that is at least above the purple area. For example, if 1200 A of welding current is required, you would need a generator with at least 150 kVA of power.
