There are pros and cons to both and much of the benefits to savings depends upon your individual air conditioning needs.
First, of all window units are air conditioners that simply sit in your window and are usually held up on a piece of wood that jut out from one of your windows. Then they plug into any standard electrical outlet in your home. There are several different models of these and you can purchase them with many different features.These are ideal for small rooms and they really put out the air and will cool your room off quickly. However, the downfall to these is that they are rather noisy and they don't keep your house at a constant temperature as does central air conditioning.Next, central air conditioning is run throughout your whole house and controlled by a central thermostat. One control will keep you whole house at the perfect temperature. It's not noisy at all and keeps your house nice and cool twenty-four hours a day. However, you will experience a higher electricity bill with central air. The cheapest bill I have ever achieved with central air conditioning was forty and fifty dollars a month, which is only at the least ten dollars more than a window air conditioning unit, but multiply ten dollars by twelve months and you're paying an extra one hundred twenty dollars a month for central air conditioning. However, it is much more convenient and many people prefer it to window units. It keeps your temperature much cooler and many think it is well worth the extra cost.