First, I added a bit of tilt using a little bit of string to allow a bit better air flow and to give it a slightly better angle to the sun. I'll be watching this carefully over the next week, which is the shortest (sun-wise) of the year!
This photo was taken on October 30th, when the outside temperature was still well above zero. Regardless, we had quite a bit of nice warmth coming from the solarium during this time. I'll post a follow-up pic soon, but today was a crisp, cold, but sunny day. The solarium quickly reached 15C without issue. Not bad since that's what my programmable thermostats are set for during the day anyway!