How many months of the year can you use an outdoor pool?

In principle, any pool can be configured for year-round use. Since a water temperature of 26 °C should be guaranteed for comfortable use, thermal energy must be supplied to the pool during the cooler months – depending on its orientation and location – and efficient insulation must be provided. The equipment can be tailored to a six-month, nine-month, or twelve-month period of use – which is ultimately a personal decision and, of course, a question of cost-effectiveness. The two initial questions are therefore: How can I supply thermal energy to my pool and how much do the individual options cost? And the second question is: How can energy loss from the pool be prevented?