Usually to attach anything to a roof involves drilling holes and putting screws in, then there's the hole for the wiring... I wouldn't mess with it on a rental house.
You CAN save a lot by switching to LED bulbs, I posted about the Cree 60 watt equiv bulbs I bought, they use 9-1/2 watts each, check out my post on them in another thread in the "off topic" folder:
LED bulbs
You CAN take those when you leave! they are even more efficient than CFL bulbs, I'm getting rid of all of my CFL's and changing over to these LEDs