As the others have said pool solar heating panels is all about surface area, all of the small panels that claim they will heat a pool are lying. For climates like ours basic unglazed black "plastic" panels work best, in fact under ideal conditions if the daytime air temperature is within about 20 degrees of the pool temperature they can approach 90% efficiency. Meaning 90% of possible heat from the sun is transferred into the water in the panel. As to the UF test results, you will find most panels are within about a 10% performance margin of each other, and that these tests are under set conditions. In the real world there are factors like wind that may allow a poorly rated flat panel under lab conditions to out perform a higher rated rippled panel, as the ripped designs do better at absorbing sunlight throughout the day if they are installed at the correct angle, vs flat panels which loose less heat to the wind.
Ike
p.s. I have a DIY install of the Techno-Solis panels (the Vortex panels mentioned above are a private label version of the Techno-Solis panels, so identical except for warranty issues, mounting brackets, and also the genuine Techno-Solis are offered in more sizes and both 1.5 and 2 inch headers, vs only 1.5 inch headers for the Vortex)
