Solar Water Heating Timeline

	1890s	First commercially-available solar water heaters produced in southern California. Initial designs were roof-mounted tanks. Later, glazed tubular solar collectors were in thermosiphon configuration. Several thousand systems were sold to homeowners.

	1920-50s	South Florida develops as a significant market for solar water heaters using mostly thermosiphon designs. Several companies serviced a market of about 50,000 homes. The industry virtually expired in 1950s, unable to compete against cheap and readily available natural gas and electric service.

	1940-70s	In Israel, Japan and Australia, commercial markets developed with manufacturing and fairly widespread use.

	1970s	The modern solar industry began when the 1973-74 oil embargo introduced its sharp rise in prices. In 1974, more than 20 companies started production of a flat plate solar collector in the US. Most were active systems with antifreeze capability. Many innovative designs were tried, but many systems were also unreliable. The industry was strengthened with the second oil embargo in 1979. Sales in 1979 were estimated at 50,000 systems.

	1980s	In 1980, Solar Rating and Certification Corp (SRCC) was established for testing and certification of solar equipment that meet standards. In 1984, one year before solar tax credits expired, an estimated over 100,000 solar hot water systems were sold. When tax credits expired in 1985, the solar domestic water industry declined significantly and sales rose around ten to twenty percent (to over 11 thousand square ft/yr) in 1989 and 1990 during the Gulf War.

	1990	Solar water heating collector manufacturing activity in the 1990s has hovered around the six to eight thousand square foot/year level since it peaked in the late-1980s and 1990.

	1995-2001	Unglazed, low-temperature solar water heaters for swimming pools have been a real success story with over 100 percent growth in square footage of collectors shipped from 1995 to 2001.

	1997-2000	NREL analysis indicates high potential interest in low-cost, polymer-based solar water heater. Two competitive solicitation ultimately yield two teams developing polymer water heaters.