Setting the thermostat at the proper temperature will save you money on your electric bill and help prevent damage to your system. The best setting for air conditioning is somewhere between 76°F and 80°F. The design temperature for most air conditioning systems is 75°F. This means that the air conditioner is not designed to cool below 75°F and setting the thermostat below this could result in damage to your equipment. If you set it lower than 76° the air does not come out any colder the system just runs longer.
For heating the thermostat should be set somewhere between 68°F and 72°F. However if your needs for comfort are outside the normal conditions, a custom designed heating and air conditioning system can be built to suit your individual needs.