The cost for an indoor swimming pool might not be as high as you think, and has become a popular alternative to outdoor pools for exercise. However, before you start planning pool parties, understand that, in many cases, average indoor pool is small – roughly 8 feet by 15 feet. How is that possible? Because of the emergence “endless pool” or “pool therapy” technologies. These technologies use adjustable waves or swim currents that a user swims against, without physically moving forward. Think of a gerbil on a wheel, now put that wheel in the pool. Some of these endless pools come equipped with treadmills and therapy jets. Since they are smaller and mostly premanufactured, costs can start around $20,000, provided you have an area that can easily be transformed. Adding an additional room or covering will obviously add to your cost. There are lots of variables, so check the prices on the indoor pool you want and get installation estimates from contractors. Installing larger pools will come with larger costs.