The air that leaks out windows and doors can account for as much as a 25% higher energy bill, since your air conditioner will have to work harder to keep the house cool in the summer and warm in the winter.
As a quick experiment, close all doors and windows in your home. Light a stick of incense and, from inside, hold it around all the cracks in your (exterior) doors and windows. If the smoke billows, it means you have a draft. Having the weather stripping repaired in drafty areas can save you loads of money, especially in Florida where the summer, and air conditioning season, lasts half the year.
A quick fix is to close drapes around east and west-facing windows, effectively blocking sunshine and heat during the long summertime days.
Another source of temperature loss is the windows themselves. They heat up during the summer and leach warmth in the winter. Double pane windows reduce this exchange significantly. You will also find that in addition to a lower energy bill, noise pollution (such as the neighbor’s lawn mower) will also be less noticeable.