The estimated impact of California’s urban water conservation mandate on electricity consumption and greenhouse gas emissions

Abstract

In April 2015, the Governor of California mandated a 25% statewide reduction in water consumption (relative to 2013 levels) by urban water suppliers. The more than 400 public water agencies affected by the regulation were also required to report monthly progress towards the conservation goal to the State Water Resources Control Board. This paper uses the reported data to assess how the water utilities have responded to this mandate and to estimate the electricity savings and greenhouse gas (GHG) emissions reductions associated with reduced operation of urban water infrastructure systems. The results show that California succeeded in saving 524 000 million gallons (MG) of water (a 24.5% decrease relative to the 2013 baseline) over the mandate period, which translates into 1830 GWh total electricity savings, and a GHG emissions reduction of 521 000 metric tonnes of carbon dioxide equivalents (MT CO 2 e). For comparison, the total electricity savings linked to water conservation are approximately 11% greater than the savings achieved by the investor-owned electricity utilities' efficiency programs for roughly the same time period, and the GHG savings represent the equivalent of taking about 111 000 cars off the road for a year. These indirect, large-scale electricity and GHG savings were achieved at costs that were competitive with existing programs that target electricity and GHG savings directly and independently. Finally, given the breadth of the results produced, we built a companion website, called 'H2Open' (https://cwee.shinyapps.io/greengov/), to this research effort that allows users to view and explore the data and results across scales, from individual water utilities to the statewide summary.

Developing a water-energy-GHG emissions modeling framework: Insights from an application to California's water system

“…For our water conservation scenario (a 20% reduction in urban use) we obtain a reduction of 17,239 GWh of savings when accounting for end-uses of water. But if we only look at the urban supply reduction, including the reduction in energy used in water conveyed to Southern California for urban uses, the reduction on electricity use is 1,663 GWh, which is really close to what Spang et al (2018) obtained.…”

“…In April 2015, the Governor of California mandated a 25% reduction in urban water use relative to 2013 levels. Spang et al (2018) obtained that this policy resulted in 1,830 GWh of electricity savings (note that they only account for water infrastructure energy use, and exclude end-uses of water). For our water conservation scenario (a 20% reduction in urban use) we obtain a reduction of 17,239 GWh of savings when accounting for end-uses of water.…”

Renewable Energy and EU 2020 Target for Energy Efficiency in the Czech Republic and Slovakia

“…Conversely, the majority of the natural gas used in the water system is used for water heating on the consumer side of the water meter. Savings varied significantly across the state's hydrological region, with the largest savings in the populous south coast region (237,200 mg) and the lowest savings in the sparsely populated North Lahontan region (1400 mg) [35]. Since the savings in electricity and greenhouse gas emissions are calculated directly from the water savings, the results of these calculations showed a similar spatial variation.…”

An Analysis of Electricity Consumption Patterns in the Water and Wastewater Sectors in South East England, UK

“…that energy-from-sludge schemes can be expanded and optimised to realise £1 billion of benefits for customers [17]. Reductions in per capita demand for water and leakages are being targeted across E&W. Although these are generally classified as water demand strategies, these schemes will yield a co-benefit of lowered energy use as it decreases the requirements on pumping and treatment systems [18][19][20]. However, the benefits would diminish in time if the overall population increases.…”

“…For example, in California, research on water-related energy use, such as that of Klein et al [24] from the California Energy Commission, as well as the studies that proceeded, led to policy-driven action to reduce electricity use in the water sector. Reductions of around 1830 GWh in 2-3 years were reported, which was mainly achieved by managing water demands [20]. However, as the literature evolved, Kenway et al [25] noted that the policy missed a much larger pool of electricity use associated with the energy used for water provisions at the household level, which is significantly greater than the energy used at the utility scale.…”