Solar hot water systems were a promising technology in the US in the late 1970's. I still have one at my house and it works just fine.
What took place? There were great subsidies. Soon the retailers were touting subsidies and selling lousy units. There was no service and much misrepresentation about quality. The subsidies were removed and the industry died.
What is the message ? I am not sure. I surmise that if the subsidies went to the manufacturers, there would have been more quality and quality control.
Israel has many very simple and sometimes home - made solar hotwater systems and they work just fine. I believe they are required to save the costs of hydrocarbon water heating and for environmental advantages.
I know most of us like subsidies for alternative energy. I am a little uncertain because of the solar hot water experience.