How they determine the actual cost varies from state to state. Some add in utilities others it only adds the rent. Where I live also factors in medical costs and being BP means they use another scale that brings the amount of rent down.
I'm going to be moving to MN if you have sec 8 as opposed to public housing you can transfer it with you. If your medical costs are high you can also factor those in for a deduction but you must keep copies of all your expenses to show proof.

The state I live in also has programs for reducing the cost of your utilities. Can't think of the name but it's though the utility company, I don't pay certain charges and do not get penalized for late payments.