Dana,

Oddly, I don't think we are too different in our opinions. We both appreciate either side can easily manipulate the numbers to justifiy their case.

I like the idea of a better "overall" solution. The combi approach is interesting. I would like to see more solar thermal applications and I can see how you could intergrate with this approach. I think a major stumbling block with solar WH is the cost to garuantee constant hot water. A solar water heater could provide 90% of your HW needs but that last 10% will cost you. Either in capital (Tankless) or standy loses with a tank heater. If you could have a combi system that could easily incorporate thermal solar plus with some heat storage options, it becomes attractive in overall energy use.