Solar energy refers to the use of the sun's rays rather than electricity, oil, kerosene or natural gas to provide heat for a wide variety of uses. Sunlight strikes and heats an "absorber" surface within a "solar collector". The water to be used flows through the absorber that has been warmed by the  sun and picks up the heat from it. An analogy is often made to a garden hose that sits in the sun and then warms the initial water passing through it.

For pool heating, a flat panel is used that is made up of many small tubes. The size and number of tubes as well as the material of the absorber effect how well the sun's warmth is captured and transferred to the pool water. (This is referred to as the thermal performance rating of the product.)

The smaller the tubes, the slower the water flows through them which in turn enables more heat to be transferred to the water. Likewise, if the number of tubes used is increased, more water can be exposed to the heat and therefore warmed. Most tubing
is made of durable, lightweight, ultraviolet-resistant polyolefin material blended with proprietary additives determined by each manufacturer.

In addition to the solar panels, the other major parts of a solar heating system include the circulation system and the storage tank. For pools, the circulation system is the pump and filter, and the storage tank is the pool itself.