If I were you I would contact my local housing athority and ask them because after reading your problem and sharing it with a friend we agreed that it doesn't seem legal what your landlord is doing. Do you have a lease or do you go month to month? Your landlord may only pay $60 a month for your gas bill and he's charging you $100 so he's making a $40 profit and if that's the case you might as well tell him you want to pay your own gas bill.