Energy is expensive and we can't be wasting. A tip for this is to put a digital thermometer near the air conditioning, so you'll know exactly the temperature you want to let the environment and can optimise the thermostat.
Many people do not know, but an armed compressor air conditioning (not only in the ventilation) spend the same energy regardless of the position of the thermostat or ambient temperature. Is the air conditioning digital or mechanical model, both work the same way (except for model reverse).
Like this, the only way to save energy is by setting the thermostat to the compressor turn on temperature considered suitable and comfortable. Where the thermometer.
This thermometer comes with a thread where is the temperature sensor. The idea is to pass this wire into the plastic part of the air conditioning, getting very close to that of air intake. Do not place near the air outlet! The idea is that if you can measure the air temperature in the room before the cooling.
Looks just like my thermometer, attached to the air intake and with the sensor (wire) inside. Cheated with is double sided adhesive.
To save energy I use the following rules:
1) Turn on the air conditioning only when the temperature is above 28 degrees.
2) Leave the thermostat at the position where the compressor disarm in 25 degrees, I consider comfortable.
Works well and it's been over a year without changing the battery. There's no lighting, IE, You can't see in the dark, but still helps to save energy. I leave below link to the product: