That depends wholly on what size lamp you intend to install in them. You can put up to 1800 watts on a 15 amp circuit, and 2400 watts on a 20 amp circuit. Also, check the label on these cans to see what the max lamp size is. I recommend sizing recessed lighting circuits for the max lamp size possible, even if you intend to install a smaller wattage lamp at first.
"Nothing is foolproof to a sufficiently talented fool"