Smart, Clean and Ready to Go: How Solar Hot Water Can Reduce Pollution and Dependence on Fossil Fuels

Mainers could cut oil and other fossil fuel use and reduce pollution through the deployment of off the shelf, cost-effective solar hot water technology. By taking advantage of this ready-to-go technology to produce hot water for homes and businesses, Maine could save more than 7 million gallons of oil and reduce global warming pollution by the equivalent of eliminating the pollution from 27,700 cars on Maine’s roads.


Environment Maine Research & Policy Center


Executive Summary

Solar water heating has the potential to reduce America’s dependence on fossil fuels and curb pollution that causes global warming and respiratory problems. By taking advantage of America’s full potential to produce hot water for homes and businesses from solar energy, the nation could reduce natural gas consumption by 2.5 percent and electricity use by nearly one percent, while avoiding 52 million metric tons of carbon dioxide pollution per year—equivalent to emissions from 13 coal-fired power plants or 9.9 million cars.

The United States should take aggressive steps to encourage the installation of solar water heaters on homes and businesses and to promote other solar water heating technologies that can make an even bigger dent in our consumption of fossil fuels.

Solar water heating is a proven technology that can reduce energy use throughout our economy.

  • Solar water heaters—which typically use rooftop collectors to capture the sun’s heat—have been in use for more than a century. Solar water heaters can replace 50 to 85 percent of the energy used for hot water and can operate in all climates.
  • Solar water heating technologies can also be used to provide hot water for industry, to provide space heating for homes or entire neighborhoods, or even to cool buildings.

Tapping America’s full potential to use solar energy for domestic and commercial hot water would reduce America’s energy use and emissions of global warming pollution.

  • Approximately 40 million homes, as well as 50 to 75 percent of all commercial roof space, can host solar water heaters, according to the National Renewable Energy Laboratory.

Achieving America’s full potential for domestic and commercial solar water heating could:

  • Save 578 billion cubic feet of natural gas, or 2.5 percent of U.S. natural gas use;
  • Save 35 billion kilowatt-hours of electricity, or just under 1 percent of U.S. consumption;
  • Prevent 52 million metric tons of carbon dioxide pollution—equivalent to emissions from 13 coal-fired power plants or 9.9 million cars.

These figures do not include potential savings from industrial solar water heating, solar space heating or solar cooling, all of which use solar collectors similar to those used to produce hot water. A European study estimated that the European Union could provide nearly half of its lowtemperature heat—which currently accounts for one-third of total energy use—with this broad range of solar thermal technologies by 2050 under an aggressive research and development scenario. 

Solar water heating delivers a variety of benefits to the economy.

  • Solar water heating could reduce energy, bills by $9.9 billion annually, saving residential customers 3.2 percent and businesses 1.6 percent of their current energy expenditures.
  • Residential solar water heaters in parts of the country pay back their initial investment in four to eight years, providing long-term savings for consumers and protecting consumers and businesses from the risk of wild swings in fossil fuel and electricity prices.
  • Solar water heating increases America’s energy security, reduces the environmental and public health costs of fossil fuel-related pollution, and creates jobs. Europe’s solar thermal industry, for example, employs 40,000 people and brings in $4.1 billion in annual sales.

Despite the recent resurgence of solar water heating in the United States, America trails far behind the world leaders in using this energy-saving technology.

  • America ranks 35th in the world for per-capita solar water heating capacity (excluding heated swimming pools), trailing such nations as Barbados, Taiwan, Tunisia and Albania.
  • On a per-capita basis, Cyprus has 83 times as much solar water heating capacity as the United States, Germany has 14 times as much, and China 10 times as much.
  • Other nations are taking the lead both in widespread adoption of solar water heating and in innovation. Solar water heaters are mandatory on most new buildings in Israel and Spain, tens of millions of solar water heaters have been installed across China, and European nations are pioneering new types of solar water heating systems that can provide even greater reductions in energy consumption.

Smart public policy can overcome the barriers to widespread adoption of solar water heating in the United States and reap the energy savings and emission reductions that would result. Local, state and federal officials should take actions to promote solar water heating, including:

  • Adoption of strong building energy codes that encourage builders to use technologies such as solar water heating to dramatically reduce fossil fuel consumption in homes and commercial buildings.
  • Adoption and implementation of strong electric and gas utility energy efficiency requirements that encourage the deployment of solar water heating and other clean energy technologies.
  • Adoption of innovative financing tools that ensure that those who install solar water heaters benefit from their investments immediately, as opposed to having to wait for years to break even on their investments.
  • Provision of financial incentives— including tax credits and grants—to reduce the cost of solar water heaters in the short-term.
  • Adoption of policies to require new homes to be “solar ready” or even to require solar water heaters on new buildings, as Hawaii has recently done.
  • Aggressive government support for solar water heating, including the installation of solar water heaters on government buildings and increased investment in research and development of solar water heating technologies.
  • Steps to develop the solar water heating industry, including workforce training programs, incentives for domestic manufacturing of solar water heating equipment, and efforts to educate the public and businesses about the benefits of solar water heating.