A common misconception associated with
thermostats is that a furnace works harder
than normal to warm the space back to a
comfortable temperature after the thermostat
has been set back, resulting in little or
no savings. This misconception has been
dispelled by years of research and numerous
studies. The fuel required to reheat a
building to a comfortable temperature is
roughly equal to the fuel saved as the
building drops to the lower temperature.
You save fuel between the time that the
temperature stabilizes at the lower level
and the next time heat is needed. So, the
longer your house remains at the lower
temperature, the more energy you save.