I read that the primary issue for similar combined water and PV systems is that it's great for making a large amount of slightly warm water, but it can't make w

I read that the primary issue for similar combined water and PV systems is that it's great for making a large amount of slightly warm water, but it can't make water hot enough for general domestic use while keeping it cold enough to improve the solar panels efficiency significantly. Also when the sun is shining, there isn't much demand for heating, so you can't use the hot water in radiators. I've heard it works well with swimming pools, as the temperature of the water required in the pool is cold enough to help the panels keep cool, and you generally want a pool to be warm on hot days in summer when you will use it most.