How to use this: Pick a scenario button at the top to get started. Then slide the controls and choose the fixtures in the cards below to match your family’s home. Everything updates right away. Your goal is to keep indoor use under 47 gallons per person per day (it drops to 42 in 2030). Check the tall bar to see what uses the most water, and look at the drought box to see if your home would pass a 20% cutback. Can you find a water bill at home? Type it in under Household to test against your family’s real numbers. When you’re done, copy the link at the bottom to save your work or share it with your class.
Your indoor gallons per person per day (blue) against the state indoor standard, which steps down from 55 to 47 to 42.
Household gallons per day, typical home in your region vs. your scenario.
Move any lever. Each change is ranked here by the gallons per day it saves for the whole household.
The link below encodes every slider. Anyone who opens it sees exactly this scenario.
Interaction pattern inspired by En-ROADS, created by Climate Interactive and MIT Sloan. Companion to the Household Carbon Simulator. Independent model, not affiliated with any utility.
Everything runs in your browser. Indoor use is built fixture by fixture; outdoor use follows California’s landscape-ordinance water budget; energy and carbon follow the water from the source, through your water heater, to the sewer plant.
The Household Water Simulator estimates how many gallons your home uses each day, fixture by fixture: showers, toilets, faucets, laundry, dishwashing, leaks and outdoor watering. It compares your result in gallons per person per day (gpcd) with California’s indoor water-use standard, and shows the hidden energy and carbon it takes to pump, treat and heat that water.
Fixture use is based on the Water Research Foundation’s Residential End Uses of Water study (2016). Fixture flow rates come from EPA WaterSense and ENERGY STAR. California’s indoor standard comes from state law (SB 1157), and outdoor estimates follow the state Model Water Efficient Landscape Ordinance. Santa Monica figures use the city’s Urban Water Management Plan. Embedded energy uses California water-energy research and EPA eGRID. See our full methods and sources.
Key sources:
Under SB 1157, California’s indoor water-use standard is 47 gallons per person per day since 2025, dropping to 42 in 2030. Outdoor watering can add a lot more, especially in summer.
Toilets, showers and faucets usually top the list, followed by laundry and leaks. Older toilets and leaky fixtures can quietly waste thousands of gallons a year.
Gallons per capita per day: the number of gallons each person in your home uses on an average day. It makes homes of different sizes easy to compare.
Pumping, treating and heating water takes electricity and gas. Hot water is the biggest piece, so shorter showers and efficient washers cut both water use and carbon.
Built and reviewed by the Accessible Sustainability Alliance, a 501(c)(3) nonprofit operated by the Wann Heritage Foundation. Last updated October 5, 2026. Results are estimates for education and planning. Questions or corrections: contact@wann.org.