NANDO/RP:
Great comments. I should clarify, the panels are 12 V, but reach peak approx 17 V.
I understand by putting them in parrallel I should get approx 24 V, which is better to minimize line loss(I could probably go with 12 Gauge instead of 10 Gauge). If I stuck with 12 V there would be more loss.
I do not what to replace both heater elements, because then I loose capacity to heat with AC. For example, we get three cloudy days, or we start having guests and increase hot water use. Brrrr.
So, I especially like RP's comment about why I need a low voltage element...dimming light bulb analogy...makes sense.
So my next step is to locate one of these elements, there are various places on line, in the neihgborhood of $50-$100, and install the system. I like that I should not need a controller, and other then a fused disconnect on the panels, and grounding, very little new gear. I have everything else except the DC element!
At some point, maybe this fall, I will look at installing some solar hot water with a heat exchanger for my radiant system...having the DC I can probably use a DC pump as well.
Thanks again,
AdobeJoe