On an annualized basis, tapwater in San Francisco costs $3.68 per cubic meter[1], which is actually approaching the rate for desalination to be cost effective.

On an annualized basis, tapwater in San Francisco costs $3.68 per cubic meter[1], which is actually approaching the rate for desalination to be cost effective. (For agriculture, it still far far (far) away.) Traditional (distillation) desalination uses too much energy (10+ kWh per m3). Reverse osmosis plants drastically reduce that, to the 3kWh range[2]. From what I remember from my now-outdated university studies, the capital cost of the membrane was more the limiting factor, as they get fouled pretty quickly. Disposal of very-high-salinity brine is also an issue. [1] https://sfpuc.org/sites/default/files/accounts-and-services/2022_23_Rates_Schedule_Water_Sewer.pdf https://sfpuc.org/sites/default/files/accounts-and-services/... says ~$10.71/unit, with each unit being 768 gallons, or 2907 litres. (there's a lower rate for the first 4 unit, which I would guess is subsidized). 10.71/2.907=$3.68 [2] https://en.wikipedia.org/wiki/Reverse_osmosis#Desalination https://en.wikipedia.org/wiki/Reverse_osmosis#Desalination