Depending on the size of the house, how well it is insulated, the age of the unit, and whether you have roof fans or high efficiency fans inside the house.
To make a general estimate a 1500sq. foot old Tampa home you will probably expect $200-$300 in the summer. It will go up as size goes up. It will go down as the age of the unit and insulation of the house improves.
It helps to not try and overcool your home. You are in Tampa...it will not be cold in the summer. Try to set it at comfortable (~78) use ceiling fans and try to have tile or terrazzo floors as they stay cooler.