Home heating question

Factual Questions
1

In General would fuel usage be about the same for these 2 situations:

1 - Inside temp kept at 70F, outside temp averaging 40F
2 - Inside temp kept at 50F, outside temp averaging 20F

If not which would use more, by how much apx, and why?

2

I wouldn’t think it would make a difference based on a first-order analysis. Here are other things to consider when doing a second-order analysis:

  1. The R-value insulation is probably a function of absolute temperature.
  2. Furnace efficiency is probably a function of absolute temperature.
  3. Radiation losses (especially through windows) is a function of absolute temperature.

What this all adds up to I don’t know…