I had the closed loop (water and methanol) on my geo system checked for freeze protection last year. The contractor told me the loop was good to -25 degrees F. I understand a heat pump isnt going to be able to operate with loop fluid temp even close to this temp, so I am not sure how this happened. It is my understanding that methanol does not conduct heat as well as water, but that it is close. I assume a loop only needs to be protected to about 15 degrees F. Am I losing a significant amount of efficiency in my geo system due to the high concentration of methanol in the loop? Just looking for ballpark number. Is it a 5% loss in efficiency or more like a 20% loss in efficiency? The loop has been like this for at least 4 years. In short, I am wondering if it is worth the high cost of getting a contractor to my home to correct the water/methanol concentration in the loop.