Yes that’s great, hot water almost for free!
During a long period of the year we get the hot water in our hose from the sun, below you see a schematic overview. We use hot water for showering, our hot-fill washer and our hot-fill dish washer. If the sun is not shining (living in the Netherlands it sometimes happens :-)) the central heater unit warms the boiler. Of course I wanted to know when I can switch off the central heater, mostly its in May.