We use solar heating system for our pool in Ontario. http://www.aesbvi.com/hotwater/poolheat.html The system uses no energy and would keep a pool very warm if there is lots of sunshine. Water is circulated up to black panels on our roof. The sun heats the roof.

Last edited by warren460; 10/02/2015 12:28 PM.
Warren S/V Scuba Doo
Lagoon 50 (winner of best crewed yacht under 55 feet at the St. Thomas crewed yacht boat show).

https://www.cyabrochure.com/ebn/2307/pdyrX/6642/4///