Using a general guideline add one 2 x 20 panel for every 5000 gallons of pool water.
How to mount solar pool panels to pallets.
In this video i m increasing safety by grounding the panels and rails.
Solar pool heating system installation manual read the complete manual before beginning the installation.
Use larger panels where possible to lower the cost per square foot.
A 12 x 24 pool might be around 10 000 gallons and would use 2 panels where a 20 x 40 pool might be slightly over 30 000 gallons and you would want as many as 6 solar panels.
To see how to calculate your pool volume read this article on swimming pool basics.
S are available in 4 x8 panel 4 x10 and 4 x12.