English: Diagram explaining how solar water heating works

Cold water enters through an inlet (A)
into an insulated storage tank (B).
From there it flows through a panel (C)
which absorbs solar radiation (D).

The solar energy is absorbed as heat and the hot water re-enters the tank where it exchanges heat with the rest of the water through convection or a heat exchanger. Hot water exits the tank at the top where it can be used (E). The temperature at the top of the tank (F+) is higher than that at the bottom (G-) because of reduced specific mass of warmer water.