Panels can face East or West, but North is a waste generally. But watch where the sun is. It moves South in the winter, and North in the summer. For me the difference is SIGNIFICANT and I turn panels on and off accordingly.

Solar heat isn't just "heat". You have to decide what you what it for, when you want it, and how much you want. Typically, salesmen tell you the panels should have a surface area near that of the pool. Like all things, this depends on what you expect of them. My panels are only about 35% of my pool's surface but they do GREAT because of what I expect them to do: Extend my swimming season to early May and mid-to-late September, and warm the pool during the summer so it isn't a shock to get in--and that's living in Northern NJ.

Most solar systems have the advantage of being easily expandable--especially the rollable panels--so you can always make a small system bigger if it is not adequate.

Solar's BIGGEST advantages are that it is basically free to operate--just the pump, but the heat is free, and it can double as a cooling system merely by running it at night. It's disadvantage is that it doesn't work without sun, or in the rain.

After having tried the opaque blue-on-top, black-on-bottom cover, the transparent blue cover, and the totally clear heavy-weight cover, I like the last best. Heavier covers insulate more and take longer to pop their bubbles. Clear covers allow the sunlight to penetrate the water and heat it directly, rather than trying to use conduction and convection currents.

Last, if you get a reel, get a good one, a metal one. I don't like the plastic ones--I had the plastic bearings self-destruct, making it hard to turn, and then the handles broke!