Heat exchangers and water heaters maintain comfortable pool temperature regardless of weather. These economical solutions use heat from a boiler or mains supply without requiring a separate heat source. Plate heat exchangers in stainless steel or titanium are suitable for salt-chlorinated pools. Electric heaters (elements) are the simplest option for smaller pools and spas — compact and easy to install. Power selection depends on pool volume and desired heating time; as a guideline, allow ~1 kW per 1 m³ of water for a continuous heater.