Low-Temperature Solar Thermal Systems: An Untapped Energy Resource in the United States

Abstract

Solar energy to heat water, to warm buildings and to provide low temperature heat for industry and agriculture is a well understood technology. Of these applications, solar hot water is the most established with a proven track record of performance. Yet in the U.S., solar water heaters are an uncommon sight on residential or commercial buildings. Various estimates put the number of installed systems at about one million (1), less than 1% of U.S. households. Many of these systems were installed decades ago during the 1970s and 1980s when federal tax incentives were in place. Today’s U.S. market for solar water heaters is far below its potential. According to one estimate, only 6000 systems were installed last year, (2), a very small fraction of the approximately 10 million gas and electric water heaters shipped each year (3).