let's talk about gas
The gas bill will range depending on the economy (it's fuel). I will say this: I had an apartment a few years back that was 2 br, 2 ba, on the third floor and about 850 sq. feet. Now, you'd think that since I was surrounded by other apartments and heat rises, my heating costs would be kept pretty low. Well, thanks to the outrageous price of fuel at the time, my one-month gas bill was $250
just for gas! Since then, I've steered clear of homes that have gas heat for that reason. I've found electricity to be much more stable in price. What you could do is ask the company who services the home for gas now for a record of gas usage for the last year and the bills. If it's a rental, ask the landlord to provide one for your budgeting purposes.
But my guess is that if you are renting/buying a 3000 square foot home, $100 here or there wouldn't be of much concern to you.
But I don't know.