I was told to call when the tank got at or below 40% especially if bad weather was expected. We called as when it was 40% and expecting bad weather.
After repeated calls and promises from them that they would "be there soon" we eventually got down to 10% with even worse weather expected. After another call, we were told that because there was some snow near our garage, that the driver refused to deliver. I asked what would happen if I ran out of propane, the customer service man said, "That is too bad." I simply clear the area off more and hope that they deliver tommorrow, like they said they would.
I am switching propane companies ASAP.