This paper provides experimental evidence that behavioral interventions spill over to untreated sectors by altering consumer choice. We use a randomized controlled trial and high-frequency data to test the effect of social norms messaging about residential water use on electricity consumption. Messaging appears to induce a small reduction in summertime electricity use. Empirical tests and household survey data support the hypothesis that this nudge alters electricity choices. An engineering simulation suggests that complementarities between appliances that use water and electricity explain roughly a quarter of the electricity reduction. Incorporating the cross-sectoral spillover increases the net benefits of the intervention substantially.
It is well-established that water infrastructure systems require energy to treat and deliver water to end-users. This fundamental relationship presents an opportunity to secure energy savings through water conservation. In a previous study, the energy savings linked to a statewide water conservation mandate in California were found comparable in both resource savings as well as cost-effectiveness to the energy savings achieved directly through energy efficiency programs. This study pursues a similar line of inquiry, but at the scale of an individual city as opposed to a statewide assessment. Los Angeles, California, serves as the case study for estimating the energy savings secured through water conservation programs relative to energy efficiency (EE) programs enacted in the study region. We apply three different estimates of energy intensity (EI) for the conversion of water savings to energy savings. These applied EI scenarios are differentiated by scale and system boundary, including: a direct assessment of EI within the water utility service territory, an expanded boundary that includes imported water infrastructure systems, and a broader, top-down estimate for the regional hydrologic zone. Across all scenarios, the estimated energy savings secured through water conservation programs prove to be cost-competitive with the energy efficiency programs enacted by the utility. When using estimates of EI with expanded system boundaries that include the upstream energy embedded in imported water supplies, water conservation becomes a significantly more attractive pathway for saving energy. This outcome underlines the importance of clearly defining the water-energy system boundary of interest, both to determine an accurate EI value, and subsequently, to design and implement cost-effective programs that jointly conserve both water and energy resources.
Energy load shifting can allow for increased renewable energy integration and reduced greenhouse gas intensity of the electricity grid. Recent research has demonstrated that wastewater treatment plants have considerable potential to shift energy loads and act as energy demand resources due to their energetic flexibility and energy production capacity. This paper investigates a wastewater treatment plant in Santa Rosa, California, participating as a demand resource on the wholesale energy market through the proxy demand resource program. Test demand response events showed that the facility was able to shift its energy load by modifying select operations without impacting wastewater effluent quality. A cost-benefit analysis based on projected program participation and the results from the test events, estimates that the Santa Rosa wastewater treatment plant could achieve up to 4.8% energy cost savings through the proxy demand resource program. Two main issues were identified from the test events: (1) the difficulty of correctly timing demand reduction periods and (2) the inaccuracy of using standard baseline methods to measure the energy load reduction. As a supplement to the case study, this paper also presents a roadmap outlining the technology necessary for wastewater treatment plants to participate in demand resource programs through energy load shifting. The roadmap identifies key instrumentation and automation infrastructure, and assets that can be utilized to provide energetic flexibility; it also recommends additional infrastructure that can stabilize energy loads and enhance controlled energy load shifting.