We are considering building a pool and looking at various heating options. We were originally looking at a pool and spa combination with NG heater. Now, I'm considering removing the gunite spa and heater to the tune of $14K and adding a Dimension 1 spa for about half that. The problem is of still like year round access to the pool. How does solar do in the winter in TX, specifically Austin? I'm wondering if I can expect to get decent increase in temps on a sunny 45-50 degree day? Anyone have any experience?