Does anyone know of an "in-line" flow meter, or gauge, to measure the volume of L.P. gas that is being used by a furnace? I've had a customer ask me about this but I'm not sure if I've seen anything other than the type of meter that natural gas companies would use for the main supply line. And I'm not sure is those type of meters could be calibrated for L.P. The issue in this situation is that the homeowner seems to be using an excessive amount of propane, (or at least the gauge on the L.P. tank says so) but doesn't believe the furnace could be using that much. The home owner is at the mercy of the propane supplier filling the tank properly and charging $$$ accordingly. I have checked the system and found that there are no leaks in any of the lines and the furnace is operationg properly with correct pressure settings and correct orifice's installed for the burners. It is a York 2-Stage furnace at @ 93.7% efficiency. (80,000 btu at high fire) The furnace is the only thing in the house using the propane and the house is also well insulated. Coldest temps in this area have been in the teens and the customer has had their 500 gal tank filled twice already this season. And now the gauge on the tank is nearing empty again. The homeowner and myself just don't believe the gauge on the tank is accurate, but the propane supplier is charging $$$ according to what the gauge says, and not the actual amount of propane in the tank. This is where it would be nice to have an in-line meter to measure exactly how much L.P. is being consumed and verify the problem with the tank. Any feedback on this issue would be greatly appreciated.