AGP Pump Speed for Solar Panels

[haybale]

I have 2 2x20' sungrabber panels and a 2 speed pump. Will I get more efficient heating with the pump on high or low?

 

[dmanb2b]

If the panels are cool to the touch in direct sun, you won't notice much difference. If high speed cools them better, it is more efficient from a heating perspective, but at the cost of utilizing more electricity.