How many hours does solar energy produce hot water?

According to the current weather in Beijing, when the sun is shining, it is enough to supply water in the morning (the water tank is empty, that is, the tap water temperature is about 10 degrees) until the water temperature reaches 40 ~ 50 degrees at 5 o'clock in the evening, but the solar energy allocated by developers is generally small, so it will not be a product with too good quality.