As others have said, it all depends on the machine title, LEDs, condition of wiring in the house, how much is going on at one time, etc... I have had 9 pins running on one circuit at once at a party with no issues. Maybe all 9 weren't being played at exactly the same time but I was definitely pushing the envelope. I bet if all 9 were in multi-ball it would have tripped the breaker. My pins are mostly LEDd and it was a newer house so I know that helped. As with anything, your mileage may vary. I know if I were building a gameroom, I wouldn't go over 6 per circuit.