The main difference is that the above ground models tend to be rated for smaller pools, since most inground pools are under 20,000 gallons. They may also use connectors that are friendlier with hoses instead of pvc pipe, as many above ground pools are plumbed with hoses. The mechanics of how they work, is the same. If your above ground pool is plumbed with hoses then you may need some adapters to install the cell, or you could elect to hard plumb the pool with pvc. The AQR-15 is rated up to 40,000 gallons so it should last a good long time.