I have a 120V electric impact wrench that pulls 7.5 Amps.
What is the lowest wattage portable generator that I can use to operate the wrench?
Watts= volts x amps
120 x 7.5= 900watts
900 watts is the supposed full load of the tool. I would add at least 20% for the generator required. That's 1080 watts. You should be looking for 1100-1200 watt unit.