The Water-Energy Nexus: Reciprocal Benefits in California’s Quest for Conservation

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“Whiskey’s for drinking, water’s for fighting over”, said Samuel Clemens. Although that has been true, it is also true that California has become a shining example of increasingly efficient and effective water use and has reaped additional energy and climate benefits in the process. 

California’s economy, politics, society and infrastructure are shaped by where there is water, where there isn’t water, and getting water from where it is to where it isn’t. 

California’s water use requires a lot of energy

The 2004 study Energy Down the Drainco-authored by the Pacific Institute and the Natural Resources Defense Council, was among the earliest reports to quantify the energy requirements for water systems in California. A 2005 study by the California Energy Commission, found that “water-related energy use consumes 19 percent of the state’s electricity, 30 percent of its natural gas, and 88 million gallons of diesel fuel every year—and this demand is growing.” Water-related energy use in California includes energy need for moving water (pumping wells, moving water through aqueducts and reservoirs, delivering water to customers), cleaning water (meeting drinking water standards, treating waste-water for discharge), or heating and cooling water (for domestic and industrial needs). Since then, other organizations and agencies have taken a closer look at the deep connection between energy and water, and what that means for both energy efficiency and de-carbonization opportunities.

Water Conservation = Energy Conservation Decarbonization

As early as 2006, immediately following the passage of AB32, CalEPA coordinated a working group to explore the benefits of energy efficiency in the water sector, and how it could support the State’s ambitious climate and clean energy goals and water-related actions in the climate action Scoping Plan. This working group was appropriately titled Water-Energy Team of the Climate Action Team (WET-CAT).

The water-energy connection is making its way into the California building code. Economic analyses and model reach codes have been developed for use with the 2016 Title 24, Part 6, and are being updated for the 2019 version of the code. California’s Energy Code, Title 20, also references the water-energy nexus. This website, hosted by the four investor owned utilities, provides helpful resources.

Although the connection was made early in the State’s climate action efforts, the value of water efficiency and water conservation came into sharp focus during the State’s 2011 – 2017 drought. Water agencies from the State-level down to local water districts, all experienced reduced energy use, as citizens and businesses all over the State responded to the drought and reduced water use by close to 25%. Using less water directly correlated to using less energy. In many cases, using less energy means reduced energy expenses. 

In a January 12, 2018 publication of Environmental Research Letters, a team from UC Davis found that in addition to saving 524,000 million gallons of water over the mandate period, state residents also saved 1830 gigawatt hours of electricity — enough to power 274,000 average homes for a year.

That electricity savings meant a reduction of 521,000 metric tons of greenhouse gases, the equivalent of taking about 110,000 cars off the road for a year, the authors wrote.

In 2016, the CPUC initiated proceeding R.13-12-011, creating four separate lines of inquiry into the connections between energy savings and water conservation, and other water management actions. The CPUC’s work resulted in a ‘water energy cost effectiveness calculator’. The calculator and other information about IOU water and energy efficiency programs can be found on the CPUC’s website. Many include rebates and incentives which may be available to local governments and other organizations. 

Although water conservation and energy conservation in water-using organizations results in the coincidental reduction of GHG emissions, until recently there was no methodology or tools to define and quantify those co-benefits. 

In 2016, the California legislature passed SB1425 (Pavley), directing the State to establish a carbon registry for the emissions averted through water conservation and water-related energy efficiency. In May of this year, CalEPA, and the Air Resources Board, after collaboration with many stakeholders and with the implementing support of The Climate Registry, launched the Water Energy Nexus GHG Registry.

The voluntary, no cost registry, provides California organizations a mechanism to measure, track, and mitigate their GHG emissions.  The Water Energy Nexus (WEN) registry is especially applicable to water agencies, local governments, and organizations with large water footprints, such as higher education and the food and beverage, hospitality, and health care industries. The WEN registry’s purpose is to assist California organizations with large water footprints become more energy efficient, reduce greenhouse gas emissions, and show their climate leadership.

Local governments seeking strategies to meet their energy efficiency and greenhouse gas emissions reductions goals should take a closer look at the benefits of systematic water conservation and management strategies, including; stormwater management, wastewater recycling, and efficient irrigation. There are now a comprehensive set of tools and resources to measure and support these water-energy-ghg emissions reduction initiatives. 


 California Energy Commission, California’s Water-Energy Relationship, Final Staff Report, CEC-700-2005-011-SF, November 2005  

 Edward S Spang1, Andrew J Holguin1 and Frank J Loge1,2 Published 12 January 2018 • © 2018 The Author(s). Published by IOP Publishing Ltd
Environmental Research LettersVolume 13Number 1