I live in a 3,500 Square Foot East Lake Victorian that was once a boiler/radiator system. But the house was converted into apartments and they installed two forced air furnace systems (one upstairs and one down). We have programmable thermostats for both and we often wonder if we are setting them too cold in their down period as it takes a while for the house to warm up.

At night, we have the 2nd floor set at 63 degrees and the 1st floor set at 50. The 1st floor kicks on around 3:30 runs nonstop for over 2 hours to get to 65 degrees. Then the same thing happens at the end of the day when we get home. It has some tech in it that allows it to calculate when it needs to turn on to have the house warm by a particular time, but I am wondering if it running for so long to warm up for such a short period of time is off setting the potential savings of it going down that low in the first place.

So, how low is too low when it comes to programmable thermostats?