The local climate, your area's electric rates, even how often doors and windows are opened and shut affect the costs to run your central air conditioner. Know the factors, so you can save money on electric bills and maintenance.
HVAC contractors and your local utility company may offer home energy audits or refer you to an independent consultant. Of course, there are some factors you cannot control, like climate. A central air conditioner will run a lot harder and get more use in Florida, than in the Northeast.
But you can lower operating costs by better insulating your home, and by keeping windows and doors to the outside shut as much as possible. Also, look at household activities and use of appliances that may require the air conditioner to work harder to cool the house.