Modeling residential water and related energy, carbon footprint and costs in California

• We model residential water use and related energy and GHG emissions in California.
• Heterogeneity in use, spatial variability and water and energy rates are accounted.
• Outdoor is more than 50% of water use but 80% of energy is used by faucet + shower.
• Variability in water and energy prices affects willingness to adopt conservation.
• Targeting high-use hoses and joint conservation policies are effective strategies.

Starting from single-family household water end-use data, this study develops an end-use model for water-use and related energy and carbon footprint using probability distributions for parameters affecting water consumption in 10 local water utilities in California. Monte Carlo simulations are used to develop a large representative sample of households to describe variability in use, with water bills for each house for different utility rate structures.The water-related energy consumption for each household realization was obtained using an energy model based on the different water end-uses, assuming probability distributions for hot-water-use for each appliance and water heater characteristics. Spatial variability is incorporated to account for average air and household water inlet temperatures and price structures for each utility. Water-related energy costs are calculated using averaged energy price for each location. CO2 emissions were derived from energy use using emission factors.Overall simulation runs assess the impact of several common conservation strategies on household water and energy use. Results show that single-family water-related CO2 emissions are 2% of overall per capita emissions, and that managing water and energy jointly can significantly reduce state greenhouse gas emissions.

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