How does 44-unit HOA share cost of utilities fairly?

We have 44 homeowners in our Illinois association. We have 8 duplex homeowners, there is a 20 unit condo building and 4 quad buildings. The association wants to make the duplex homeowners pay a portion of the utility bills for the condo and quad buildings even though we have our own individual meter we pay separately. The condo building has a master meter for those 20 units and the quads have a meter in each of their buildings. In the past,only those 36 homeowners who used those meters paid into the utility reserve portion in the budget. They now want the duplex owners to pay almost 4% each of that expense. Is this a common expense to all 44 homeowners when the 8 duplex homeowners receive their own bills and pay directly. We do not have any access to these buildings or use of the utilities. Why should we have to pay our own water bill and electric bill and then a part of theirs too?