Water-Energy Nexus and Importance of Storage

Water use and energy use are inextricably related. The extraction, treatment, distribution and use of water, and the collection and treatment of wastewater, require a significant amount of energy. Conversely, hydroelectric and thermometric power generation require large amounts of water. Water can be used to store energy economically. For example, Hawaii has a fleet of 500 grid-enabled heat pump water heaters that store energy during the day when there is an excess of renewables on the grid.


The water-energy nexus. Click here for more information and image credit.

It is important when addressing the significant issues facing San Mateo County regarding the sustainable use of both energy and water resources, to engage with diverse stakeholders such as customers, communities, suppliers, investors, employees, public interest groups and outside experts. San Mateo County Energy and Water Strategy 2025 suggests three actions that have both energy and water benefits and therefore result in the highest impacts possible across all sectors:

  1. Develop water-to-energy projects by identifying locations of existing or new large volume water movement with energy-generation capacity
  2. Develop large water tanks, including grid-enabled heat pump water heaters, for energy storage
  3. Deploy counterflow wastewater heat exchangers in multifamily or mixed-use buildings

Resources for Water Conservation

 United States Environmental Protection Agency’s WaterSense Program

WaterSense is a voluntary partnership program sponsored by the EPA.  It is both a label for water-efficient products and a resource for helping people save water. The WaterSense label makes it simple to find water-efficient products, new homes and programs that meet the EPA’s criteria for efficiency and performance. WaterSense-labeled products and services are certified to use at least 20 percent less water, save energy and perform as well as or better than regular models. WaterSense partners with manufacturers, retailers and distributors, home builders, irrigation professionals and utilities to bring the program to local communities.

San Mateo Resource Conservation District Technical Assistance

The San Mateo Resource Conservation District (SMRCD) is a trusted source of information for technical assistance and resource management facilitation on water conservation. With a competent staff of experienced conservation specialists, SMRCD provides comprehensive, integrated technical services addressing water issues to meet the needs of private and public land owners, land managers, public agencies, interest groups and others in San Mateo County. Free, confidential technical assistance helps landowners and land managers manage natural resources.

Bay Area Water Supply and Conservation Agency (BAWSCA) Rebates, Tips and Classes

The Bay Area Water Supply and Conservation Agency (BAWSCA) offers a variety of rebates and programs to help Bay Area water users become more water efficient inside their homes and outdoors. BAWSCA provides simple tips to reduce indoor and outdoor water use, classes on water conservation and landscape education and a water-wise gardening guide that shows how to garden beautifully while saving water.

Leak Detection Pilot Study by WaterNow Alliance

San Mateo County participates with other local leaders in the WaterNow Alliance to achieve high-impact, widespread adoption of sustainablewater solutions in local communities. Residents of Foster City and Burlingame are currently eligible to participate in a leak detection study and pilot leak detection devices in their homes. These devices are monitored for their effectiveness in detecting active leaks and enabling remote water shutoff, as well as for their impacts on water conservation behavior. The findings from the study will be helpful in forming countywide efforts on water conservation.

Green Business Program: The San Mateo County Office of Sustainability certifies and promotes small- to medium-sized businesses that operate in an environmentally responsible manner through the county’s Green Business Program. By offering technical assistance and resources, the county helps local businesses save money by teaching them how to conserve energy and water, minimize waste, prevent pollution and shrink their carbon footprints. The program, which is part of the California Green Business Network, is available in the following sectors: office/retail, restaurant/catering, hotel, cleaning services, auto repair, small manufacturing, printing and medical/dental practices. Click here to learn more and to participate in this program.

Water Agencies in San Mateo County

There are many water agencies in San Mateo County. Residents of most cities receive water from the city or a special district within the city. They can contact their City Hall for more information about water rebates. California Water Services Company provides water service to San Carlos, the city of San Mateo and South San Francisco. Its rebate programs can be found here. Many water providers from cities or the California Water Services Department also offer rebates.

San Mateo County Check-It-Out Home Energy and Water Saving Toolkit

San Mateo County Energy Watch offers  a Check-It-Out Home Energy and Water Saving Toolkit with free resources that community members can borrow from any public library in the county. It is designed to help residents perform a basic assessment of the efficiency of their home energy and water use and improve it where possible. This program also aims to help residents save money on their utility bills and increase the comfort of their homes.  The toolkit user guide includes information on how energy and water are used in homes and steps that can be taken to reduce use of both.

Brisbane and Pacifica Reduce Energy Requirements and Greenhouse Gases

Brisbane and Pacifica are two San Mateo County cities making notable improvements in reducing their energy requirements and GHG emissions. Brisbane uses a solar thermal cover for its community pool and a variable frequency drive for the circulating pump to reduce conventional energy use and global greenhouse gases. Solar thermal heating provides 10 to 20 percent of the energy needed to heat the pool, depending on weather.

Pacifica improved heating and lighting in its Council Chambers while reducing its utility costs. Rather than replacing a broken boiler system with a traditional central heating system, the city installed a ductless “mini-split” heat pump to save energy and make the building’s temperature more comfortable for occupants. This pump prevents 30 percent of the energy from being lost by pushing heated air through leaky and bulky ducts. Pacifica also improved lighting quality in the Council Chambers by replacing more than 100 outdated light bulbs with highly efficient LED lighting. It is expected that this action will reduce the building’s annual energy use by 22,000 kilowatt hours, saving the city 10 percent on the building’s electricity costs each year and trimming the city’s carbon footprint by almost 16 metric tons of carbon dioxide a year – the equivalent of the pollution from more than three cars for one year.[1] These projects are small steps toward reaching each city’s goal of significantly reducing greenhouse gas emissions and their carbon footprints.

Solar Swimming Pool Heaters

Solar swimming pool heaters are cost competitive with both gas and heat pump pool heaters and can significantly reduce swimming pool heating costs and annual operating costs while reducing GHG emissions. With a solar swimming pool heating solution, pool water is pumped through a filter and then through a solar collector, where it is heated and then returned to the pool. This system requires little maintenance and roof space and has a long lifespan. However, solar swimming pool heaters are less efficient in the evening and on overcast days than a traditional pool heating system, require more up-front cost and can take a bit longer to initially heat a pool. For image credit, click here.

Water-Efficient Landscaping Ordinances

Water poses one of the most difficult-to-achieve building and landscaping efficiencies. Local codes and state guidelines regulate the safe disposal of gray water and sewage from buildings. Houses or buildings that strive to safely recycle, treat and reuse water on-site often face regulatory challenges that go beyond simple building permits. With water shortages in some states becoming the norm, changes to these regulations may be a step toward allowing buildings to become more water efficient. Other building efficiencies that face regulatory challenges include on-site wind generation and solar panels on constricted sites that could otherwise be used for reforestation or retaining/increasing tree canopies.

According to the California Department of Water Resources, about half of all urban water use is for landscape irrigation in California, and large water savings can be gained by efficient landscape design, installation and maintenance. The State of California publishes and maintains the Model Water Efficient Landscape Ordinance (MWELO) for use by local governments. MWELO’s purpose is to promote the values and benefits of landscaping practices that integrate conservation and efficient use of water. The model ordinance establishes a structure for planning, designing, installing, maintaining and managing water-efficient landscapes in new construction and rehabilitated projects. Multiple municipalities in San Mateo County, including Menlo Park, San Mateo, Millbrae and Brisbane, have adopted water-efficient landscaping ordinances based on this model.

Water Reuse

Landscape Design Assistance Programs. These programs support water conservation in landscaping by supporting water customers’ transition from turf lawns to water-efficient landscaping. Many cities offer turf conversion rebates that are often underutilized, especially considering their financial benefit to customers. Supplementary design assistance programs increase participation in these programs and make attractive, user-friendly and sustainable lawns more accessible. Many San Mateo County water districts already participate in the Bay Area Water Supply and Conservation Agency’s (BAWSCA’s) Lawn Be Gone program, which offers a rebate of $1 to $4 per square foot of turf removed from lawns.

Satellite Treatment Facility. Satellite plants are an ideal solution for businesses looking to improve water resilience when they are far away from treatment plants and centralized recycled water pipelines. By treating water closer to its source and next to its destination, satellite plants and their pipelines also form smaller, more energy-efficient circuits. In 2020 the Sharon Heights Golf and Country Club in Menlo Park completed construction of a satellite treatment facility. This plant will replace up to 400,000 gallons of freshwater a day with recycled water that would otherwise be treated and released into San Francisco Bay.

Rain Barrel Rebate. Rain barrels capture roof runoff to be saved and used for irrigation or other non-potable purposes. Rainwater reuse is a simple, cost-effective way for water customers to engage in water sustainability. Just 1,000 square feet of roof surface can capture 625 gallons of water per inch of rainfall. Depending on the size of a rain barrel and how often it is utilized, a San Mateo County household could save more than 11,000 gallons per year. Harvesting rainwater using a rain barrel not only saves money and water for irrigation, but also helps prevent stormwater pollution from urban runoff and moderates flooding. Click here to learn more about the Flows to Bay rain barrel rebate program and image credit.

Gray Water and Purple Pipes. Gray water is gently used water from bathroom sinks, showers, tubs and washing machines, i.e., all streams except for the wastewater from toilets. It can be used for landscaping, crop irrigation and other non-potable purposes. Local ordinances could encourage or mandate use of this reclaimed water for public landscaping and irrigation. The San Francisco Public Utilities Commission has a thorough Graywater Design Manual for homeowners and professionals who want to install residential graywater systems for subsurface outdoor irrigation. Additionally, new construction and significant remodels could be required to install an option for “purple pipes” that carry reclaimed water from bathrooms and laundry rooms to landscaped areas. Image credit.

Ecology Action has proposed an ordinance requiring residential property owners doing major construction to build dual-drainage plumbing and dual water supply-graywater systems into their home construction and remodeling projects. Greywater Action is a collaborative of educators who teach residents and tradespeople about affordable and simple household water systems that dramatically reduce water use and foster sustainable cultures of water. Its teaching tools include interactive models of composting toilets and graywater systems, design and installation workshops, and presentations.

Stormwater Pollution

As rain, stormwater and irrigation runoff flow across impervious surfaces like rooftops, paved roads and even oversaturated lawns, they pick up and carry pollutants such as litter, animal waste, sediment, pesticides, motor oil and other urban chemicals.  This untreated stormwater runoff and other sources of “outdoor drainage” create stormwater pollution that typically flows into street drains, then into San Mateo County streams and creeks, and ultimately into San Francisco Bay and the Pacific Ocean, making these waterways unsafe for recreational contact and fishing and for creatures that live in them. San Mateo County cities are required by law to prevent contamination of stormwater by utilizing clean work practices, inspecting businesses and construction activities, and educating the public. The San Mateo Countywide Water Pollution Prevention Program (SMCWPPP) is a comprehensive countywide effort to prevent stormwater pollution. For image credit, click here.

Rainwater harvesting is the collection of runoff from a structure or other impervious surface “at the source” in order to store it for later use. Traditionally, this involves harvesting rain from a roof. Gutters channel the water into downspouts and then into storage vessels. Rainwater collection conserves clean water for animals or landscape plants, reduces stormwater runoff from homes and businesses, and protects local creeks, San Francisco Bay and the Pacific Ocean by reducing urban runoff that transports litter, motor oil, copper and other pollutants into storm drains. BAWSCA and participating member agencies are partnering with SMCWPPP to offer rebates for the purchase and installation of qualifying rain barrels.


[1] https://smcenergywatch.org/category/case-study/