An air conditioner unit that has a 3 ton capacity uses approximately 3500 watts of electricity in an average hour.An air conditioner unit that has a 3 ton capacity uses approximately 3500 watts of electricity in an average hour. Therefore, divide this wattage by power factor=3500/0.80=4375VA. Hence, we need to select 4.5KVA generator to run this 3 ton AC.