How about my air conditioning bill? Your typical stick house (which is our affectionate term for conventional 2”x4” framing) has R-11 rated insulation in the walls and R-19 in the ceiling. So you say “What’s the R value of a log?” the answer is it doesn’t have one. Logs have thermal mass. Whole logs are big and it takes lots of energy to heat them up and a long time at that. Then once heated up it takes a long time for them to cool down. In effect your home is always 180 out of sink with the outside. Real log homes are cool during the day while the sun heats them up, then at night when it’s cool outside your log home is warm. It takes very little energy from you to keep it comfortable inside. Personally I have one very small wood burning stove and a window unit. We live in East Texas and our friends laugh and then get that serious look when we compare electric bills with their stick frame homes.