Unfortunately, at least in the US, desalination cost is dominated by the high cost of capital, not by the cost of the energy. For example, the largest desal pl

Unfortunately, at least in the US, desalination cost is dominated by the high cost of capital, not by the cost of the energy. For example, the largest desal plant in the US is the Carlsbad plant in California [1]. For our purposes, it's a very nice plant, because the numbers are very round: it cost $1 BN to build. It has an output of 190k cubic meters per day, or 5.7 million m3 per month. The plant was funded with bonds. Let's say you want to build it today. A private person has access to 30y mortgage rates of about 7.7%. But this being a large corporation, and using municipal bonds that are tax exempt, let's say you can borrow at 5.5%. If you plug in a mortgage calculator, that comes to $5.7 MM per month, which is very fortunate, or a very round $1.00 per m3. The energy use of desalination is in the range of 2.5 to 4.0 kWh per m3 ([2], page 91). Let's say it is 4.0 for the Carlsbad plant (to be conservative; most likely it is lower). The average cost of electricity for US industrial users is $0.0775 [4], so that's about 19 cents per m3. Recap: $1.00 capex cost per m3, $0.19 electricity cost per m3. Increasing the efficiency of desalination by a factor of 2 would not make desalinated water twice as cheap, but only about 10% cheaper. There is an asterisk here though: I don't know why, but the cost of electricity in California is much higher than the average cost in the US. It costs 18 cents vs 7.75 cents. So, for the particular case of California, the capex cost still dominates, but not by a factor of 5, only by a factor of 2. [1] https://en.wikipedia.org/wiki/Claude_%22Bud%22_Lewis_Carlsbad_Desalination_Plant https://en.wikipedia.org/wiki/Claude_%22Bud%22_Lewis_Carlsba... [2] https://www.energy.gov/sites/default/files/2019/09/f66/73355-7.pdf https://www.energy.gov/sites/default/files/2019/09/f66/73355... [3] https://www.amtaorg.com/wp-content/uploads/07_Membrane_Desalination_Power_Usage_Put_In_Perspective.pdf https://www.amtaorg.com/wp-content/uploads/07_Membrane_Desal... [4] https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a https://www.eia.gov/electricity/monthly/epm_table_grapher.ph...