Photo: A solar water heater sits on a tiled roof
A solar water heater sits on a tiled roof in Greece.

Photograph by Jeff Morgan / Alamy

Environmental Impacts

Each type of water heater has its own pros and cons. This list of green options explores the impacts of each.

Tankless Systems: Tankless, or on-demand, water heaters can cut energy use by 30 percent using one simple concept: Rather than continually heating a tank full of water, which sits unused in the basement for hours on end, tankless systems heat water only when it’s needed. And, hot water never runs out, even when your teenager takes an extra-long shower.

Tankless heaters last an average of 20 years, longer than most storage-tank systems, so they don’t end up in landfills as often. However, as with all green products, usage is a critical factor. An endless supply of hot water might tempt some owners to increase demand—and decrease their green savings.

Solar Heaters: The sun is the oldest water heating system there is—and it’s making a comeback. The U.S. Department of Energy estimates that more than 1.5 million U.S. homes and businesses heat their water with the sun—and more than 94 percent of them call those systems a good investment.

Mother Earth agrees. Solar heaters produce zero greenhouse gas emissions. You could save some 50 tons of CO2 during the 20-year lifespan of a typical solar water heater.

Most Energy Star-certified solar heat systems are used with gas or electric backup, so users needn’t worry about being caught without hot water. To make the most of a solar heater, mount it on a suitable roof that faces south and receives direct sunlight during the late morning and afternoon hours. And sure, being in the Sun Belt helps efficiency—but it’s not necessary.

“Germany is a leader in solar water heating and that’s not exactly an ideal climate for it,” says Lane Burt, a building energy engineer at the Natural Resources Defense Council.

Solar heaters can be expensive. Even if it cuts your annual costs in half, you may need a decade to recoup the cost. But federal and state tax incentives are making these systems more affordable. Then there’s the added bonus of showing off your rooftop tank, which is becoming a bit of a green status symbol.

« What to Look For | Usage Tips »


Save Water

Learn More About Freshwater »


  • change-the-course-dry-co.jpg

    Help Save the Colorado River

    NG's new Change the Course campaign launches. When individuals pledge to use less water in their own lives, our partners carry out restoration work in the Colorado River Basin.

  • National Geographic headquarters in Washington, D.C.

    Sustainability at National Geographic

    The National Geographic Society aims to be an international leader for global conservation and environmental sustainability. Learn more about the Society's green philosophy and initiatives.

Learn More About Freshwater »