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Volume 15, Issue 22 ~ May 31 - June 6, 2007

Got an Environmental Question? Send it to: EARTH TALK, c/o E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881. Or submit your question at: Or e-mail us at: [email protected].

From the Editors of E/The Environmental Magazine

Slash Greenhouse Gases with Solar Power

A solar water heater will do the Earth — and your wallet — good

I heard that using a solar powered water heater in my home would reduce my CO2 emissions significantly. Is this true? And what are the costs?

—Anthony Gerst, Wapello, Iowa

An average four-person household with an electric water heater needs about 6,400 kilowatt-hours of electricity per year to heat its water, according to mechanical engineers at the University of Wisconsin’s Solar Energy Laboratory. Assuming the electricity is generated by a typical power plant with an efficiency of around 30 percent, it means that the average electric water heater is responsible for about eight tons of carbon dioxide annually, which is almost double that emitted by a typical modern automobile.

The same family of four using either a natural gas or oil-fired water heater will contribute about two tons of carbon dioxide emissions annually in heating their water.

Surprising as it may seem, analysts believe that the annual total carbon dioxide produced by residential water heaters throughout North America is roughly equal to that produced by all of the cars and light trucks driving around the continent. Another way of looking at it: If half of all households used solar water heaters, the reduction in carbon dioxide emissions would be the same as doubling the fuel-efficiency of all cars.

That might not be such a tall order. According to the Environmental and Energy Study Institute, 1.5 million solar water heaters are already in use in U.S. homes and businesses. Systems can work in any climate. The Institute estimates that 40 percent of all U.S. homes have sufficient access to sunlight such that 29 million additional solar heaters could be installed right now.

Another great reason to make the switch is a financial one. Residential solar water heating systems cost between $1,500 and $3,500 compared to $150 to $450 for electric and gas heaters, according to the Environmental and Energy Study Institute. But with savings in electricity or natural gas, solar water heaters pay for themselves within four to eight years. They last between 15 and 40 years — the same as conventional systems — so after that initial payback period is up, zero energy cost essentially means having free hot water for years to come.

What’s more, in 2005 the U.S. began offering homeowners tax credits of up to 30 percent (capped at $2,000) of the cost of installing a solar water heater. The credit is not available for swimming pool or hot tub heaters, and the system must be certified by the Solar Rating and Certification Corporation.

Zoning and building codes relating to the installation of solar water heaters usually reside at the local level, the U.S. Department of Energy’s Consumer’s Guide to Renewable Energy and Energy Efficiency reports, so consumers should research the standards for their own communities and hire a certified installer familiar with local requirements. Homeowners beware: Most municipalities require a building permit for the installation of a solar hot water heater onto an existing house.


For more information:

• U.S. Department of Energy:

Got an environmental question? Send it to: EarthTalk, c/o E/The Environmental Magazine, P.O. Box 5098, Westport, CT 06881; submit it at or e-mail [email protected]. Read past columns at:

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