Since the early 1970s, the efficiency and reliability of solar heating systems and collectors have increased greatly, and costs have dropped. Today's solar thermal systems are used for solar water heating, solar pool heating, and in solar space heating.  Solar collector is the key component of a solar heating system. Solar collectors gather the sun's energy, transform its radiation into heat, then transfer that heat to water, solar fluid, or air. There are several types of solar collectors including flat-plate collectors, evacuated-tube collectors, and integral collector-storage systems.  Flat-plate collectors are commonly used in residential water heating systems.

The basic design of a solar geyser is based on a collector box assembly situated below a storage tank. Within the box is an absorber made of black copper sheets, to the back of which are attached copper pipelines. The absorber is covered with a transparent glass and insulated at the back and sides to reduce heat losses. The collector works like a miniature greenhouse trapping heat that is transferred to the water in the pipes. Cold water flows from the bottom of the storage tank to the collector, from which heated water rises to the top of the storage tank. To maintain the functioning of the system, a constant supply of cold water must be available, for which an overhead storage tank on the roof is convenient.

The most common applications of solar heating include:

one of the most cost-effective ways to include renewable technologies into a building is by incorporating solar hot water. A typical residential solar water-heating system reduces the need for conventional water heating by about two-thirds. It minimizes the expense of electricity or fossil fuel to heat the water and reduces the associated environmental impacts. Solar water heating projects are generally simple, reasonably inexpensive, and can be completed in a day or two. Everyone should have a solar water heating system.

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Pool heating

in a solar pool-heating system, the existing pool filtration system pumps pool water through the solar collector, and the collected heat is transferred directly to the pool water. Solar pool-heating collectors operate just slightly warmer than the surrounding air temperature and typically use inexpensive, unglazed, low-temperature collectors made from specially formulated plastic materials. Glazed (glass-covered) solar collectors are not typically used in pool-heating applications, except for indoor pools, hot tubs, or spas in colder climates. In some cases, unglazed copper or copper-aluminum solar collectors are used.

Space heating

solar space-heating system can consist of a passive system, an active system, or a combination of both. Active solar space-heating systems consist of collectors that collect and absorb solar radiation combined with electric fans or pumps to transfer and distribute that solar heat. Active systems also generally have an energy-storage system to provide heat when the sun is not shining. The two basic types of active solar space-heating systems use either liquid or air as the heat-transfer medium in their solar energy collectors. Passive solar space heating takes advantage of warmth from the sun through design features and it usually involves new construction.     

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