You will need to have your pool water tested for salt before you determine how much to add. All water has 'some' salt present. Then you use the pool calculator to figure out how much salt to add. Once you know how many bags you'll need you can compare salt prices and estimate how much it will cost (I have no idea on that- no SWG
). You can use the "Google search" feature-bottom left corner, to search for info on salt, there are several threads that discuss cost and where to buy it, pool salt, vs. water softener salt - etc.
Once the salt is in there, unless there is significant water replacement, it should last you the entire season. You may need to add a little, from time to time, but it's not significant. When you winterize at the end of the season, you drain down some of the water. Then in the spring, you have to raise the water level back up, which means the salt level may be diluted, so you'll have to add a little bit then.
The solar panels will be fine with the SWG, many folks use them. Make sure you have a bypass valve. You want to not run the solar at night, as I believe that has the opposite effect - of cooling the water.
They make timers specifically for pool pumps with multiple settings - check at the pool store or one of the online pool retailers, or even amazon.
