[cabmandone]

Here's the deal:
In order to pay the least amount for propane you need to own your own tank. You also want to make sure you have enough storage to get you through the winter to fill at summer rates (normally). Figure out your normal natural gas usage for a year and convert that to gallons. Then figure out what the tanks are going to cost you to own.

Absent the above, you want to make sure the company providing the propane doesn't have you on auto fill because they'll come out based on degree days to top you off in the winter when prices are the highest. You want to be in "will call" if they'll let you but that means checking your percentages, understanding your usage, and knowing when to call in before you run out.