Volts x amps x .80. So 1x15 amp circuit wired 120 = 1440. 15a x 120v = 1800 x .8 = 1440 watts safely on that circuit while staying withing code and not causing a fire hazard. So assuming you are going to run new circuits from your circuit breaker and you have 200 amp service and space available you would need 1 circuit for every two lights and you might be able to get a couple fans on the same circuit depending on rating of the fans. If you we're to use larger gauge wire and wire the circuit 220v instead of 120 your lights would require a different receptical like your electric oven, dryer or water heater or some larger air conditioners but you increase the load capability on each circuit. 40a x 220 x .8 = 7040 watts so you still need more than one circuit On top of that You still need enough juice in the house. If you have 100amp service forget 13x600 watt lights unless the house is otherwise unoccupied.