Pumping ocean water through reverse osmosis filters to remove the salt in a quest to produce drinking water takes a lot of energy, observes Heather Cooley, Pacific Institute water program co-director. On average, she says, desalination requires 15,000 kWh of power/million gallons of freshwater produced. This means that Poseidon’s plants in Carlsbad and Huntington Beach, each sized to produce 50 million gallons of water/day, would need the same amount of energy when operating at full capacity as 39,000 people use on average. If all of the desalination plants proposed in California ultimately were built—a prospect considered unlikely—they would consume about the same amount of power as a city with more than 250,000 people, based on Pacific Institute data. Not surprisingly, notes Cooley, the cost of the all that energy generally makes desalination the most expensive way to produce new drinking water, considerably higher cost than efficiency or even recycling in most cases.