What is a Solar Water Heater?

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Two features, a collector and a storage tank, characterize most solar water heaters. Beyond these common features, solar water-heating systems can vary significantly in design. The various system designs can be classified as passive or active and as direct (also called open loop) or indirect (also called closed loop).

This article below was extracted from Dept of Energy publication (DOE)  ... Through specially designed systems, energy from the sun can be used to heat water for your home. Depending on climate and water use, a properly designed, installed, and maintained solar water heater can meet from half to nearly all of a home's hot water demand.

Passive systems operate without pumps and controls and can be more reliable, more durable, easier to maintain, longer lasting, and less expensive to operate than active systems. Active solar water heaters incorporate pumps and controls to move heat-transfer fluids from the collectors to the storage tanks.

Both active and passive solar water-heating systems often require conventional water heaters as backups, or the solar systems function as pre-heaters for the conventional units. A direct solar water-heating system circulates household water through collectors and is not appropriate in climates in which freezing temperatures occur. An indirect system should not experience problems with freezing because the fluid in the collectors is usually a form of antifreeze.

If you are considering purchasing a solar water-heating system, you may want to compare products from different manufacturers. The Solar Rating and Certification Corporation  provides a benchmark for comparing the performance of some solar water heating systems.

The Solar Rating and Certification Corporation publishes performance ratings of both solar water-heating systems and individual solar collectors. These published ratings are the results of independent, third-party laboratory testing of these products. All systems and collectors that have been certified by the Solar Rating and Certification Corporation will bear the Solar Rating and Certification Corporation label.

Keep in mind, though, that simply having an Solar Rating and Certification Corporation label does not imply that the product has a superior performance. Carefully compare Solar Rating and Certification Corporation label information on different brands and models to ensure that you are fully aware of projected performance.

Before buying nay water heater consider the advantages both financial and convenience of the different types ... would you rather have a storage or tankless heater for example. The table below compares the 2 types briefly ...

Just choosing a solar water heater with good ratings is not enough, though. Proper design, sizing, installation, and maintenance are also critical to ensure efficient system performance.

Although the purchase and installation prices of solar water heaters are usually higher than those of conventional types, operating costs are much lower.

Hot Water System feature variables Tankless hot water system features Storage tank hot water system features
Energy cost Lower cost ... reduced energy losses Higher losses ... higher energy usage
Unit size Much smaller than hot water storage tank Large compared to tankless hot water heater
Installation cost Small compared to storage tank heater in new structures but higher in retrofit More complex to install in new structures
Installation space Compact unit .. saves space taken up by storage tank hot water heater which can be used as closet for example Bulky heater and tank system with difficult access normally
Capacity When large quantities are required simultaneously flow can reduce or temperature of water is reduced Normally depending on size of tank capacity is higher for simultaneous use

The one common factor in choosing any system is the cost of the energy source. Note that this can change dramatically in a short space of time and especially in winter months. A second factor is the energy factor which really determines how efficiently the equipment utilizes the energy used to heat the hot water.

NOTE Since this article was written energy costs have skyrocketed making it very economical to install hot water heaters using solar power.