Turning down the furnace temperature will save energy. The amount of energy it will save depends on things like the setback duration, number of degrees, and the climate you live in (the warmer the climate the more you will save with a setback).
For heating, you can try the "6-8" thermostat setting method. Set your thermostat at 68 degrees Fahrenheit. This temperature is considered an optimum energy conserving setting for most homes. When you're away or sleeping for 6-8 hours, reduce the thermostat setting by 6-8 degrees. Whether turning the thermostat back manually, or by using an automatic setback thermostat, you will save energy and allow yourself to reduce heating bills.
