We have hot water heater, furnace and stove on propane, and their bills were getting ridiculous too. Somehow there was NO way we were using that much.
So, I started cooking on an electric skillet, we installed a wood burning stove, turned down the hot water heater and documented all of that! Miraculously the following month our bill was still as high as before....so, we went out, bought our own regulator and tanks, filled them, and hooked our own stuff up to the house.
When on our own tanks we were averaging (for 7 people with showers, laundry and cooking) 5 gallons a week!!!
I had not paid on their bill for a few weeks and when he came to "lock out" the tank so we would have "NO" propane, that would mean no heat or cooking to them, even with children in the house!!! A$$holes!!
I said, no worries, take your tank and shove it, we don't use it anymore anyway because we were tired of you ripping us off!!
I would really look into where it is going if I were you!
Good luck!
Mommy