I'll paste some of my previous posts below that you may find helpful. You won't regret adding solar once it's all installed and working. We don't use our solar cover in the summer here and Friday night was kind of cool (low 70's) for here. Yesterday we ran the solar in the morning and brought the pool up from 80 to 88 by about noon. (air temp was 90 and full sun on pool to help out). We had 3 families over in and out of the pool all afternoon until about 10:30pm and the water only dipped to about 85 by the time everyone was done with the pool. We haven't been using our solar since early June I think. Nice to have when you want it though.
Posts are below:
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The plumbing was a lilttle confusing at first look, but after some planning time to throroughly understand how it all has to work it turned out pretty simple and our system works well. One good resource that has good "cartoons" and videos explaining the whole thing is h2otsun industries.
http://www.h2otsun.com/pools/index.html
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You are in TN, so I would think that you have enough available sun to go with solar. Check sites that sell solar for their recommendations for your location and pool size. I only have limited experience with this, but so far, initial purchase price is about the only cost involved. This makes it the best long term option IMHO. You can automate it so you don't even have to think about it once it is set. You don't really even need the air to be all that warm since it is the same principle as a water hose laying out in the sun. Even on a cool day, the sun heats the water that's been sitting in the hose and you feel the heat as soon as you turn on the water. Solar panels do this far more effectively than the water hose I just described though. It's been a long time since college physics, but I'm pretty sure that this is the 1st law of thermodynamics. In lay terms, heat goes from where it is to where it isn't. I had a nerd moment there.
Back to researching your options, We researched various heating options during our decision as well (search our other posts to see more about that.) Anyway, we went with solar in early April and the DIY install was fairly easy. It can be done in a few days if you plan it out well before you begin. The cost for everything in our system was under $2000. Our air temps were in the upper 70's to upper 80's in the day when we started using it and within a few days our pool went from about 72 to holding 85. We used our solar cover when not swimming to prevent heat loss and help maintian the temp over night - lows back then were 50's mostly. By mid May we were at 90 daily without using the cover. We now have it set at 88 and it holds that fine. BTW, we have 5 Aquasol panels 4' x 12' roof mounted on a south facing roof. We get full sun on the panels over 8 hours a day. Since we run the pump about 10 hours a day anyway, the purchase price was the only real cost we've seen so far. 5 panels is actually 1 less than the minimum recommended for our size pool and our location, but so far it's working fine for us. I can easily add 3 more if needed and may add to our system in the fall once we can determine if that will extend pool use enough to justify it. Hope this helps you in your research.
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(context of this one was bubbles out of the returns when solar is on) -- We just installed our pool this year so my experience is limited, but if you have a cartridge filter, when is the last time you cleaned your filter? The filter catches a lot of debris from the initial pool installation as well as when you vaccum. We begin getting bubbles from the solar air relief valves on our system about the same time the filter gets dirty. 30psi is the magic number for us. We had a big party for the kids this weekend with about 30 kids in & out all day and that was enough to require filter cleaning.
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(Mounting solar panels on the roof) -- I just did my DIY solar install a few weeks ago (automated and all that) and agree with all above on the holes. I wrestled mentally with the idea of putting holes into a roof that does not leak. I discussed it with a roofer I know and felt better about the whole process after that. You can't make an omelet without breaking some eggs, so you'll just have to go for it. Buy high quality sealer and keep a couple of old t-shirt sized rags on the roof with you as you work. That sealer is very messy and I promise that you WILL need the rags. Goo Gone and GoJo work well for getting it off of your hands at the end of the day. I hear that latex surgical gloves are a good clean hands option as well. (I just got dirty and used the aforementioned cleaners after the fact.)
Here's how you safe yourself on the roof: get a decent climbing rope for you and something adequate for your tool bag. Tie the ropes off to an immovable object (a tree works well) on the opposite side of your house from where you are working and take the rope over the peak of the roof so it hangs down on the side you need to work on. Tie yourself off with this (70's Batman & Robin climbing style). Use caribeaners to clip yourself in and make adjustments etc. so you can easily move around. Once you are secure up there it gets pretty fun. There's rock climbing sites out there that can show you how to tie off & secure yourself --it is really easy to do, keeps you safe, and frees up both hands and your mind so you can work efficiently and effectively. Now, for the cheaper grade rope, get yourself a tool bag and load it with all the things you may need up there. Pull it up to the roof and tie it off. You can use dummy chord on things you may drop and break (drills and such). You may want to use gloves depending on roof temp so you don't burn yourself. Having lots of pockets is a plus too..they come in very handy on the roof. Oh, and get good galvanized lag bolts, you don't want rust up there.
Now that you're tied off and safe, working with the panels on the roof can be a pain as well. You can preset them by tieing them off with ropes so you don't have to hold and drill at the same time. I did not have a helper up there, so I had to get creative on how to make it happen. I tied my panels off and pulled them up to the roof, then tied them in to my ropes to hold them where I wanted so I could align them, drill, and bolt. It went pretty smoothly. Basically, I pulled a page from some things I had been trained on in the past and applied it creatively to my project. Hope this keeps you safe and helps you out. I installed 5 each 4' x 12' panels this way. Oh, you'll need to use the schedule 40 PVC to connect it all together. Just get white pipes (unless you have black available in your area) and paint them black with the plastic formula spray paint for the pipes that will go on the roof. I cut and dry fit all of my pipes, then I glued my roof pipes in sections and painted them on the ground. After they had adequate time to dry, I took them up to the roof and installed them. I scratched them in some places so minor touch-up painting was all I had to do on the roof...simple to do. I initially made the mistake of using black ABS pipe to span a skylight and learned that ABS is a bad choice...the hard way. There's always time to do it again...the right way. Good luck with your install.
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There were some others as well, but these seem relevant. I've only installed solar once, so that's all the experience I have at it but I'm happy to share what I learned. If you nave questions about what I did on ours just ask. (PM to get my attn) Best of luck to you!
I've had so many problems with the pump and such that I haven't had a chance to put these up. So I would love it if you would give step by step directions on what you do. At this point, I will most likely wait until Spring but am kinda clueless on how to do this but don't care to pay someone to do something that I have every confidence in myself to do. So....keeps us posted! Pictures would be FABULOUS! Good luck! 
though it is now cloudy 
:lol: I very much appreciate this thread!