I will use 100%. I will be heating the hot tub come summer they need to be about 103 degrees! so I do have a year round use for the heat. And the collector will go to the roof come summer also oriented @ my lattitude + 23 degrees? I think? It's printed upstairs in a file somewhere, I'll find it when it's time. I will be setting it directly into the solar noon winter sun. As for the water tank there is only my wife & I so some preheating is all I'm after if it's free I'll take it. [ Parent ]