At this time (2018-2019), the region has experienced extremely high rainfall, with reservoirs filled to the brim. But just last year, we were concerned about the lack of rain, how much water we can save, and in that context, how much energy and greenhouse gases are produced when moving water to us here in the San Diego region.
The water-energy relationship first appeared in a 2005 California Energy Commission (CEC) study which stated that the “water-related energy consumption is large — 19 percent (%) of all electricity used in California” (Table 1-1 p.8, CEC 2005). A more recent study (Spang, 2018, UC Davis) found that electricity savings from mandated statewide water conservation measures from July — September 2015 were almost identical to the first-year electricity savings in the period July 2015–June 2016 from energy efficiency investments by all of the state’s Investor-owned Utilities (IOUs) — a dramatic savings. Though this effect was unintended because the purpose of the mandate was to conserve water, it demonstrated the important role that water conservation can play in energy conservation in California.
However, the story about how much energy is used for water may be quite different at the city level compared with the state-level, not least because definitions of water-energy components vary from state to water district to city-level depending on whether it is about water planning or about climate action planning. Previously we showed some general relationships on water-energy especially in the City of San Diego. This post continues and delves deeper into the relationships between water use and energy use at the state level contrasted with that at the city level (San Diego region), the “city” being a common unit used for climate action planning.
Energy Embedded in Water at the State versus City Level
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