We have this one, and love that it takes table salt, so we can store very small amounts of salt,
Bill and Helen have to recharge about every 2 to 3 weeks, according to Bill. We have to recharge once a week.
Recharging frequency will depend on how hard the water really is and how much you use. We use a lot, yorkie baths take a lot of water. We do not have a washer and dryer, Bill and Helen do.
Here is a URL
http://www.portablewatersoftener.com/
They have a real intersting map showing where water is harder, or not.
As Helen states, would not be without it!
Carol