Yes, that's a savings. The more the temperature difference between inside and outside the more you have to heat (or A/C) in the summer. Your furnace will run less during the day versus how hard it will work to bring it back up to temperature. This assumes you're gone for a while so the 58 degree setting is in place for a bit.How does everyone handle their thermostat in extreme cold like this? I typically drop mine to 58 while I'm at work and then fire it up about 30 minutes before I head home. I see mixed opinions on whether or not that is actually an efficient method to reduce cost.