In my case I set back 2 degrees. I have found that a 5 degree set back takes too long to get back to temp at my house (several hours). You would be surprised how much less the stoker runs even at a 2 degree difference. The thing about my house (open design) is what ever temp the t-stat is reading the rest of my house is already at this temp. If I put my setback at 5 degrees I have to heat the entire 2000sqft with a 14ft high vaulted ceiling in the living room back up 5 degrees and it takes quite a while. I would think that anything more than a 5* setback would cause you to use the same amount or more coal to bring it back to temp.