When completed, the Carlsbad desalination plant will convert 50 million gallons of water a day into drinking water, about 7-10% of San Diego’s needs, and will be the biggest desal plant in the Western Hemisphere.
Water from the plant will cost about double what the Los Angeles Metropolitan Water District charges. However, it guarantees San Diego will always have at least some water. 100 millions gallon a day will be pumped in from the ocean, filtered to 50 million gallons of drinking water, with the brine then being diluted and pumped back into the ocean.
Modern desal systems use 50% less electricity than previous methods. Even with that though, desalination still uses lots of power. As always, electricity and water are inextricably bound in California.