It obviously depends on the apartment, but over the past year my bills have ranged from a low of $52 in the summer to a high of $163 in the winter. The average has been about $106.
Note that I only use gas for heat, but National Grid charges about $15/month for the gas connection regardless of use. Thus, in the summer, I pay for gas without using any. You will actually be better off using gas for cooking because you get a certain amount of supply for free with your fixed delivery costs, so you will not be paying for supply that you never use.