Cost of Natural Gas vs. Propane for a Patio Heater??? I am looking at buying 2 patio heaters. Can anyone report...

I am looking at buying 2 patio heaters. Can anyone report me the efficiency/cost difference of using Natural Gas as opposed to Propane. I will be using the heaters through February simply and would be going through approximately $100 of propane per week while using the heaters over the winter. The Natural Gas heater costs nearly 50% more than the propane heater, but would I bring in up the cost in using unprocessed gas?
Answers:    Wow!......... What a question.......Efficiency...... ummmm let's see, that would be a big 0%. You're heat the great outdoors, probably not the most efficient point in the world to be doing.

Now contained by regards to your cost of operation press; it's unanswerable without knowing the raw gas rates in your nouns.
The natural gas will cost 150 per week.They burn close to like peas in a pod.