The California Aqueduct transports water from Northern to Southern California.
The California Aqueduct transports water from Northern to Southern California.

Approximately 65% of the California’s water supply is in Northern California while 65% of water demand is in Southern California.  California’s water conveyance system requires an enormous amount of energy to transport water through hundreds of miles of canals and pipelines and dozens of pump stations from the north to the south.   Water treatment, distribution and wastewater treatment also require significant energy. A set of studies recently completed for the California Public Utilities Commission estimated that about 7.7% of the state’s total electricity requirements are used every year by the water infrastructure. 

A simple diagram of the water use cycle is used as a framework for identifying and qualifying opportunities to optimize the net resource, economic and environmental benefits of the state’s water and energy resources and infrastructure. Opportunities to optimize water and energy in combination exist in all segments of the water use cycle.

California's Water Cycle

To help quantify the opportunities for energy savings in the water sector, the CEC introduced the concept of energy intensity as a means of expressing the relative magnitude of water-energy relationships.

“Energy intensity is defined as the amount of energy consumed per unit of water to perform water management-related actions such as desalting, pumping, pressurizing, groundwater extraction, conveyance, and treatment - for example, the number of kilowatt-hours consumed per million gallons (kWh/MG) of water. This concept is applied to water supplies, to components of the water use cycle, and to the total energy intensity of a unit of water throughout the entire water use cycle.1

The energy intensity of future water supplies (marginal supplies) is expected to increase dramatically due to increased pumping requirements, higher treatment energy use by brackish and seawater desalination, and more stringent treatment requirements for discharge of wastewater.  For example, the average energy intensity of untreated water supplied to Southern California is approximately 3,500 kWh/MG; however, the energy intensity of marginal supplies ranges from 3,500 to 12,200 kWh/MG.  

Key strategies to keep energy costs from sharply increasing as a result of increased reliance on marginal water supplies include: conserving water, investing in energy efficient water infrastructure, new technologies to reduce energy use by marginal supplies, and expanding the use of recycled water (a less energy intensive supply).  Additional actions are detailed in the next section: Measures.


1California Energy Commission. California’s Water-Energy Relationship. CEC-700-2005-011-SF. November 2005.

The life cycle of water; from collection and production, to treatment, delivery to end uses, consumption, and for treatment of wastewater that is either recycled or discharged.
  • On-Site Water Recycling Policy Brief

  • On-Site Water Generation

  • Best Practices Study

  • Recycled Water Study

  • On-Site Water Recycling Policy Brief

    California continues to face various challenges in reliably meeting its demand for water. As population increases and the aging water infrastructure becomes less efficient, drought and water scarcity remain long-term concerns. Water recycling is thereby emphasized in California policies and mandates as one way to alleviate some of the uncertainties in the future water supply. A 2012 Alliance Huntington Beach study found that on-site recycled water systems can supply water at lower energy intensity than imported water and desalination in Southern California. Such on-site technologies can be a good fit for developers interested in reducing the water consumption of new commercial and municipal buildings. In addition, the customization options of the systems are appealing, and the cost is incremental as compared to larger municipal water recycling and desalination efforts.

    Nevertheless, on-site water recycling is a relatively new concept and doesn’t fit neatly into existing jurisdictions overseeing water-recycling and water- and waste-water treatment. Figuring out who has jurisdiction can be tricky for project developers as well as for those charged with preserving public health and safety. Still, the demand for non-potable water for uses like flushing toilets and irrigating landscapes could be met by recycled water, and frameworks have been developed to enable on-site water recycling to meet those needs.

    In December 2013, the Alliance completed a study entitled California On-Site Water Recycling: Policy Brief that documents the barriers to implementing on-site water recycling systems and also presents potential solutions. The policy brief focuses on these barriers:

    • Lack of clear information about how to apply for permits
    • Expensive daily coliform laboratory sampling and analysis
    • Stringent certification requirements for system operators

    Key study conclusions include:

    ·      On-site recycled water systems are an emerging technology with the potential to play a role in helping manage California’s increasing water scarcity. 

    ·      Immediate actions should be taken to perform additional work on understanding potential regulatory models, estimating benefits, and initiating pilot activity.

    ·      An information portal should be designed so that potential developers of on-site water recycling systems and staff at key agencies have access to detailed information. 

    ·      One stretch goal to work towards is an exception to the Title 22 requirement for daily coliform sampling for on-site water recycling systems with a track-record of high water quality.

    The study also highlights a number of case studies as examples of on-site water recycling. Download  the full report for more details.


  • On-Site Water Generation

    California water supplies are stressed as a result of decreasing supply and increasing demand.  While conservation and efficiency are the most cost effective solutions, they may not completely solve the problem. Water recycling is an additional solution that is applicable across the entire state and can produce a relatively consistent resource regardless of the season or weather.  Wherever there is a wastewater treatment plant there is an opportunity to generate a local, sustainable supply of recycled water.  Indeed, generating recycled water is not a challenge, distributing it is.  A major barrier to implementing a successful regional recycled water system is the cost of distribution pipelines.

    Recycled water can be implemented on a smaller scale; generating water in the same location as its demand eliminates the need for expensive distribution systems. Similarly, rainwater harvesting can also provide a local, low-cost supply of water. On-site water generation (both recycling and rainwater harvesting) has the potential to not only conserve water but save energy used by supply and distribution infrastructure.

    In December 2012, the Alliance completed a study entitled On-Site Water Generation: An Analysis of Options and Case Study  that documents the characteristics of the on-site water generation systems and also conducts a detailed cost benefit analysis for a representative case study on the City of Huntington Beach. The study sought to understand:

    • Types of technologies available to provide on-site water generation.
    • Costs and benefit analysis of the on-site water generation options.
    • Primary market barriers to technology adoption.

    Key study conclusions include:

    • On-site recycled water systems can supply water at lower energy intensity than imported water and desalination in Southern California. 
    • On-site recycled water systems are most cost-effective in larger capacities. 
    • On-site water recycling can provide more water than rainwater harvesting. 
    • Rainwater harvesting systems are more cost effective in areas with a good balance of supply (rain) and demand throughout the year.

    The study also discusses a number of recommendations for California policy-makers to stimulate the production and use of on-site water generation. Download the full report for more details.

  • Best Practices Study

    In 2010 the California Public Utilities Commission completed a series of studies and pilot projects documenting significant opportunities for reducing the energy requirements of the water sector (including production, treatment, distribution and water conservation.) To build upon this, the Alliance developed the Eastern Municipal Water District: A Case Study of Best-In-Class Water-Energy Programs and Practices report documenting for retail water and waste-water agencies:

    • The range of potential energy efficiency and generation opportunities that could be implemented;
    • The types of programs and technologies available to help water agencies achieve energy benefits; and
    • The primary barriers that need to be overcome to increase adoption of “best” energy programs, practices and technologies. 

    The Eastern Municipal Water District (EMWD) serves as a case study to illustrate the types of strategies and measures California water agencies can implement to improve energy efficiency.  In the case study, the Alliance documented EMWD’s progressive implementation of multiple best practice strategies and interviewed operations staff to document barriers and lessons learned.

    Key findings from this study include:

    • A close relationship between water agencies and energy utilities is instrumental to achieving energy savings in the water sector; 
    • Smart meters and SCADA can provide large amounts of data to baseline the energy use of water agency; however, availability of detailed data is not required to identify promising energy saving opportunities.  A simple bill analysis could still lead to savings.
    • Technology risk and the need for investment prioritization may prevent water agencies from installing certain efficiency measures.
    • Newly adopted South Coast Air Quality Management District emissions limits may prevent water agencies from continuing to beneficially use biogas; complying with new limits may prove cost prohibitive for some water agencies.

    Download the full report for more details.

    Wastewater treatment plants have multiple options to reduce energy use
    Wastewater treatment plants have multiple options to reduce energy use
  • Recycled Water Study

    In the U.S., many non-potable uses are served by potable water that has been treated to safe drinking water standards established by the federal Environmental Protection Agency and state and local agencies charged with protecting public health and safety.  Recycled water can be used to safely displace use of potable water for these types of non-potable uses such as toilet flushing, landscape irrigation, commercial car washing, and fire protection. 

    Recycled water is produced by treating municipal wastewater.  California treated about 5 million acre-feet of municipal wastewater in 2002.  About half of that amount was recoverable as recycled water.  However, as much as 70% is discharged without beneficial use to natural waterways and to the ocean every year, representing a viable, untapped resource – a lost opportunity.

    Recycled water could be used to enhance potable supplies after undergoing highly advanced treatment. Several water agencies in Southern California are taking advantage of advanced technologies to produce recycled water that exceeds California drinking water standards.  These agencies are using this recycled water to protect and replenish groundwater aquifers that serve as a major potable supply to the region. 

    In May 2008, the Alliance released a study titled The Role of Recycled Water in Energy Efficiency and Greenhouse Gas Reduction that estimated the potential energy and carbon benefits of accelerating and increasing the development and use of recycled water in Southern California.

    Results of the study show up to 580,000 acre-feet of existing recycled water supply in Southern California is currently being released to streams and the ocean without benefit.  This supply could meet all of Southern California’s projected increase in water use through 20301 . According to the study, every gallon of recycled water that is not used to offset potable water use is a missed opportunity for California to increase water and energy supplies and to reduce carbon emissions.

    Download the full report for more information.  See the appendices for profiles of each of the participating water agencies.

    1As projected by the Department of Water Resources under a Business As Usual scenario

    Water Treatment Plant Operator holding a sample of recycled water
    Water Treatment Plant Operator holding a sample of recycled water