I are now living in Houston Texas and summer time temperatures tend to be in the 90's for several months of the entire year. The home of mine is fairly new and has a good quality core HVAC system. In spite of very much of the air conditioning of mine is done by the more mature technology of a room or "best portable ac for car, %domain_as_name% blog entry," window unit.
The room unit of mine is a 12,500 BTU Energy Star model that cost you aproximatelly $260. It is not rated to be as efficient as my central unit but utilizes less power per BTU in the opinion of mine. This is because it doesn't run a significant fan to blow air with the entire home. We run the window model from aproximatelly 8PM to 8PM on warm days. When we're not home the central product is shut down and the window device will keep the home aproximatelly 15 degrees cooler compared to the outside for our 1,900 sq ft house. It also keeps the moisture low. We supplement the window product when we're home with the main AC. Cooling the home this way decreases our energy costs. We finally run the central unit about 50 % less, thus it needs to have an extended life. On the very hot days, when managing the window product and also the central device, we get additional cooling power.
In Texas it is a major deal when the central AC of yours fails throughout the summer months. We run a second 12,000 BTU device once the central AC is broken. That makes the house livable during the fix time.
Another advantage of getting window AC units happens when there's a power failure. Windstorms as well as hurricanes are frequent in the Houston area. We like getting a generator and window AC units as insurance for power failures. During IKE we ran 2 window products by generator for a week, together with the fridge, microwave, as well as some lights.