Oil Lamps

I have read a LOT about these lately. I am curious if anyone knows if it really is more cost effective to use these instead of electricity. ESPECIALLY now with the more energy efficient bulbs.

I recently found a post on how to make your own oil lamp that will burn using any food grade oil- including fat from chicken (what a great way to use up chicken fat!).

If you did not have to buy the oil, the wick would be the only thing you would be paying for (even if you make it yourself, you still have to pay for materials). But still, I am curious about cost. I know it is very quaint to use them, and maybe just by using them you would not be turning on as many lights or leaving lights on while not in the room. Maybe that is where the cost saving comes in?

Does anyone know??