As Los Angeles pushes for local water, new study explores trade-offs for county’s energy needs

Researchers point to high energy requirements of residential water heating

By Emily Castelazo

Los Angeles County imports most of its water from distant sources, which is energy-intensive and leaves the region’s water supply vulnerable to disasters like earthquakes. 

As Los Angeles County moves toward sourcing more of its water locally, a team of researchers from UCLA and across California have published an analysis of how targeted changes in water supply could affect the county’s energy needs, as well as the significant energy requirements of residential water heating.  

The county has committed to sourcing 80% of its water locally by 2045, which means further boosting alternative sources such as recycled water. Los Angeles County has also committed to achieving carbon neutrality by 2050.

“If we want to meet our goals of having all local water, we need to treat it, and advanced water treatment for direct, potable reuse is more energy-intensive,” said Felicia Federico, executive director of the California Center for Sustainable Communities at UCLA and an author of the study. “There are definitely trade-offs.”

The researchers showed that combining water conservation with alternative local supplies, such as water reuse or stormwater capture, can reduce energy consumption and the intensity of water management in Los Angeles.

The study, published in Environmental Research Communications, will help regional policymakers plan for the energy needs of the transition to more local water. Researchers evaluated the county’s energy needs for urban water management by evaluating planning scenarios to estimate energy requirements of importing water, pumping groundwater, distributing water through pipes, treating water and wastewater, and heating water in homes.

“This study is meant to contribute to California’s statewide efforts to reduce greenhouse gas emissions and energy use,” said Erik Porse, the report’s lead author and a visiting assistant researcher at UCLA’s California Center for Sustainable Communities.

The collaborative study also involved researchers from USC, UC Davis, UC Berkeley, and the Public Policy Institute of California. The methodology is publicly available for other cities that want to replicate the study.

The most energy-intensive part of water management? Heating water in homes

While imported water is energy-intensive, heating water in homes uses much more energy. In Los Angeles, 40% of natural gas used in homes goes to heat water for bathing, laundry and other uses. As a key piece of the energy-water nexus, the study also quantified total energy use for residential water heating and compared it to utility operations. In Los Angeles, as in other cities, household water heaters use more energy in total than utility companies use to treat and transport the water.

“It’s interesting that energy for household water heating is significantly larger than the energy needs for the utilities to move the water around,” Federico said. “It’s important to put those in perspective to understand where you can have the most impact overall for energy and water savings.” 

Eric Fournier, one of the study’s authors and the acting research director for the California Center for Sustainable Communities at UCLA, said he hopes the study helps regional policymakers recognize the importance of reducing energy and water consumption in the face of climate change.

For everyday Angelenos, Fournier said that conserving water and using energy-efficient water heating equipment when possible are two lifestyle changes that can reduce water and energy consumption. “Generally, be conscious that the consumption of water is in a very real way the consumption of energy,” Fournier said.  

Read the full study.

This research was supported by the National Science Foundation, the Los Angeles Bureau of Sanitation, and the Office of Water Programs at Sacramento State University.

Study authors:

Alvar Escriva-Bou, Water Policy Center, Public Policy Institute of California

Felicia Federico, California Center for Sustainable Communities at UCLA

Eric D. Fournier, California Center for Sustainable Communities at UCLA

Mark Gold, Institute of the Environment and Sustainability at UCLA, California Natural Resources Agency

Kathryn B. Mika, Institute of the Environment and Sustainability at UCLA

Stephanie Pincetl, California Center for Sustainable Communities at UCLA

Erik Porse, California State University, Sacramento; California Center for Sustainable Communities at UCLA

Kelly T. Sanders, Sonny Astani Department of Civil and Environmental Engineering, USC

Edward Spang, Department of Food Science and Technology and the Center for Water and Energy Efficiency, UC Davis

Jennifer Stokes-Draut, Department of Civil and Environmental Engineering and ReNUWIt Engineering Research Center, UC Berkeley