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Benefits & Impacts of California’s Indoor Water Use Standard
A multi-university study evaluating how California’s 2030 indoor residential water use standard may affect water supply, wastewater, recycled water, and affordability across the state.
Led by the California Institute for Water Resources within UC Agriculture and Natural Resources, the research team is working with the California Department of Water Resources to quantify the benefits and impacts of increased indoor water-use efficiency and inform long-term implementation of Senate Bill 1157.
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Project Snapshot
Project Period
May 2025 – January 2028
Study Area
Statewide · California
Project Lead
California Institute for Water Resources
State Partner
California Department of Water Resources
Why This Study Matters
California’s urban water-use efficiency framework requires urban retail water suppliers to meet water-use objectives based on statewide efficiency standards. Senate Bill 1157 updated the indoor residential water use standard and directed the California Department of Water Resources, in coordination with the State Water Resources Control Board, to evaluate the effects of the lower standard.
The study examines how greater indoor water-use efficiency may influence not only future water demand, but also wastewater flows, recycled water production, infrastructure planning, system finances, and affordability.
What the Research Will Examine
The multi-university team is evaluating four connected dimensions of California’s transition toward more efficient indoor residential water use.
Future Urban Water Demand
Forecast future water demand and efficiency trends in California cities as indoor water use continues to change.
Water & Wastewater Connections
Evaluate how lower indoor water demand may affect wastewater generation, collection, treatment, and system operations.
Recycled Water Production
Assess potential impacts of reduced indoor water use on wastewater flows that support recycled water production and reuse.
Affordability & System Impacts
Examine financial and affordability implications for water, wastewater, and recycled water systems across California.
From “Making Conservation a Way of Life” to SB 1157
In 2018, California adopted Assembly Bill 1668 and Senate Bill 606, establishing a long-term framework for urban water-use efficiency. Urban retail water suppliers use statewide efficiency standards as part of their annual water-use objectives.
Senate Bill 1157, enacted in 2022, updated the indoor residential water-use standard and required additional analysis of the benefits and impacts of the 2030 standard on California’s water supply, wastewater, and recycled water systems.
Research Team
The project brings together expertise in urban water management, wastewater, recycled water, economics, engineering, public policy, and affordability from institutions across California.
California Institute for Water Resources · UC ANR
Erik Porse
Rachel Shellabarger
Hope Hauptman
Camilo Salcedo
Sacramento State · Office of Water Programs
Brian Currier
Dakota Keene
Caitlyn Leo
Harold Leverenz
UC Merced · Civil Engineering
Colleen Naughton
UC Riverside · School of Public Policy
Kurt Schwabe
UCLA · Luskin Center for Innovation
Gregory Pierce
Grace Harrison
UCLA · Civil & Environmental Engineering
David Jassby
Public Engagement & Working Groups
DWR is incorporating input from technical advisory panels and working groups that include representatives from industry, government, research institutions, nonprofit organizations, and other interested parties. Working group meetings are open to the public.
2026
April 27, 2026 · Virtual
SB 1157 Benefits & Impacts Working Group Meeting #3 →
January 15, 2026 · Virtual
SB 1157 Benefits & Impacts Working Group Meeting #2 →
2025
September 29, 2025 · Virtual
SB 1157 Benefits & Impacts Working Group Kickoff Meeting →
Project Timeline
2022
Senate Bill 1157 updates California’s indoor residential water-use standard and directs DWR to evaluate its benefits and impacts.
2025
Multi-university research begins in May. The Benefits & Impacts Working Group holds its public kickoff meeting in September.
2026–2027
Research, modeling, technical review, and stakeholder engagement continue.
January 2028
The research team is scheduled to provide study findings to the California Department of Water Resources.
Project Resources
DWR · Urban Water Use Efficiency Standards & Studies →
Background information on California’s urban water-use efficiency framework, indoor residential water-use studies, and related legislative requirements.
UCLA Luskin Center for Innovation · Current Water Research →
Information on the project’s wastewater, recycled water, and affordability research.
CIWR · SB 1157 Research Study Announcement →
Original project announcement and research team overview.
Connect with CIWR
Learn more about CIWR’s urban water research, research partnerships, and ongoing work on water-use efficiency and conservation in California.