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.
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).
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 preheaters 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 & Certification Corporation (SRCC) provides a benchmark for comparing the performance of some solar water heating systems.
The SRCC 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 SRCC will bear the SRCC label.
Keep in mind, though, that simply having an SRCC label does not imply that the product has a superior performance. Carefully compare SRCC label information on different brands and models to ensure that you are fully aware of projected performance.
The Florida Solar Energy Center (FSEC) also provides information on solar manufacturers and contractors. It also maintains solar equipment testing facilities and publishes performance ratings for solar water heating systems.
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.