Kerosene vs. Natural Gas

With NG prices expected to increase 15-40% this winter, I was concidering doing the majority of the heating w/ a kerosene heater.
Looking over the NG bill, I see that the price gets lower the more I use. I will always use some for cooking and drying. If I heat solely by kero. it might mean that I will never get any NG at the discounted rate.
I would like to know which would cost less. I know this dep[ends on the price of the 2 and the efficency of the 2 heaters, but is one far and away more costly?

A word of caution: Be very careful with kerosene heaters. Personally I would never use any combustion system that was not vented outdoors. You can find Kerosene heaters that are vented outdoors but I do not think they would be a solution for a temporary thing which seems to be what you are looking for.

before I used a non-vented kerosene heater, I would try to save by lowering the temperature or heating only parts of the house.