most households are using very little electricity from the hours of about midnight to 7 am. Besides refrigerators (which only use very little wattage when sitting throughout the night) and figure a few lights left on (60-100w each) and maybe a fan on all night is another 100w. So some 1000w lighting systems would look very suspicious left on 24 hours a day, so 18/6 setups might be a good idea if you are going that route.