It would be a little more but not allot, it depends on how much equipment you run on the tank. The extra expense is not really gonna be the electric in my opinion but you do have extra money going out for food, test kits to check the water, and some extra on the water bill if you don't have a well and water conditioners to keep the water safe for the fish.
And if a filter breaks or lights have to be replaced they can be expensive to replace