Bestway Pool Heater is simple and effective to warm up water in your above-ground swimming pool, transforming it into a comfortable and relaxing space to swim, paddle and play in. The pool heater is powered by an electrical outlet. It comes with two hoses and attachments, one of which connects the heater to a filter pump and the other to a pool. Water is pumped into the heater via the filter pump, warmed up as it passes through and then pumped back into the pool. The heater is compatible with pools measuring 15ft or smaller (water volume of 400-500 gal) and filter pumps or sand filters with a flow rate of 1,000 gal/hr. (3,785L). Depending on pool size and water temperature the heater can take anywhere from 12 hours to 3 days to reach your desired temperature. If clambering into a freezing pool is making you look and feel blue then the Bestway Pool Heater is the accessory for you!