This is our 2nd Season Heating with a Propane Furnace... I Misplaced the Formula to calculate daily consumption so we can watch the Cost to Heat.. We have 2 / 465 litre tanks for a total of 930 litre's , but due to Delivery regulations the Tanks can only be filled to 80% capacity or 744 litre's.. From this point I'm drawing a Blank, From the Date on the Delivery Ticket counting X number of days and the reading on the Dials on top of tanks..? Help Appreciated , Cheers Thanks..