Domestic solar hot water (DSHW) systems consist of several basic components. The two most prominent are (1) the solar panels or collectors, and (2) the water storage tank. The solar panels are usually located on the roof or on the ground next to a house. In both locations, they need to be positioned so they receive full sunlight year-round. The water storage tank is typically located next to the conventional water heater, often located in the basement of a home. Copper pipes connect the collectors with the storage tank, and various pumps, sensors, and controls ensure that the system works automatically. Because many DSHW systems utilize pumps, they are classified as “active systems.” (As you shall soon see, though, there are a few DSHW systems that require no pumps at all.)

Solar hot water systems work in all climates, from the sunniest areas (the Sunbelt) to the dreariest of all climate zones (the so-called Gloom Belts). The type of system you install depends on the climate, as you shall soon see.
With this overview in mind, let’s take a look at your options, starting with the simplest of all systems. Table 3-1 provides a useful summary of the types of systems. Before we begin, though, permit me to make one more point vital to your understanding of domestic solar hot water systems.

As you shall soon see, domestic solar hot water systems fit into one of two broad categories: direct or indirect. Direct systems heat water that you use. Indirect systems heat a fluid that then heats the water you use. For reasons that will be clear shortly, direct systems are also referred to as open-loop systems; indirect systems are referred to as closed-loop systems.