Responce to PM question:
First, you might want to read the sticky that I wrote some time ago that is here:
http://troublefreepools.com/viewtopic.p ... highlight=
Also, I have a pump basics paper in the pool school section that might be helpful. Both explain some of the tradeoffs with pumps and the hydraulics sticky explains how to read pump head curves and what they mean.
Next take a look at this web site which shows the performance of the superpump:
http://www.poolplaza.com/Super-Pump-techspecs.shtml
As you can see, all of the pumps have a maximum head of well over 15 feet. This means that any of the pumps will raise the water that much and much more so 15 ft is not a problem for any pump.
Now look at the low speed performance. All will also be able to lift water to 15 at low speed although at a much lower flow rate. Most panels require 40-60 GPM for top efficiency so low speed, although possible, will not give you enough flow for an efficient solar panel.
In the hydraulics sticky, it expains what happens a low speed of a two speed pump but basically, the flow rate is halved and the effective HP is 1/8 of full speed. Head loss is about 1/4 of full speed.
[EDIT] One addition thing I neglected to mention was that pump HP choice is dependent on several things but primarily on the maximum desired flow rate. While the 1/2 HP superpump may be able to prime the panels, the resultant flow rate may not be enough for efficient solar panel use. Here are examples of flow rates for 1 1/2" plumbing and various HP for the Superpump:
1/2 HP - 35 GPM
3/4 HP - 38 GPM
1 HP - 42 GPM
1 1/2 HP - 45 GPM
2 HP - 50 GPM
Your flow rates may be different but this gives you an idea of how they change with HP. Also, the Superpump II will have higher flow rates for each of the pump HP.
So 1 1/2 HP would be more than enough flow rate and the 3/4 HP would be the minimum that you would want for solar but it depends on the panel requirements.
What is your current filter pressure and pump HP/SF and/or model ?
Also, how long are the runs from pool to pad?
And, are there separate pipes from pool to pad for each return or are they both fed off the same pipe run?