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).
Often people will lower the thermostat to 50 - 60 degrees Fahrenheit while away. Then turn it up to 65 - 70 degrees Fahrenheit when they are at home. It is also important to change your central air conditioning air filters and to have the units serviced by a professional for maximum efficiency.