Another thing to remember is the humidity levels. During this period, dendrobiums do not need a lot of moisture. Very little water will be enough to keep their roots alive. Also keep in mind that their roots constantly need plenty of air circulation so you should place them where there is a lot of fresh air.
Remember, that is based on energy usage, not comfort-levels, which are the purpose of having an air conditioner, in my not-so-humble opinion. Fact: At night, the ideal temperature comfort range for Americans drops to 65 to 72 degrees Fahrenheit (or about 87 degrees if you are my wife).
Try 78 Degrees: 78 degrees is a good point for an air conditioner to run at its optimal performance level. Think of it as a car on cruise control headed across the flat Midwest prairie. It's not chugging along going uphill, it's just plugging away, steady as she goes.