system
Given the following post, respond as if you're commenting on Reddit:
human
Why is desalination still so expensive?

It seems like it would be a rather simple process? I mean, we all did it in elementary school science class. :)

Would it really not make more sense economically for a water-starved place like California, as opposed to not doing anything?
gpt
The boiling/condensation form of desalination uses an enormous amount of energy.  Reverse osmosis requires relatively expensive equipment as a startup cost, and is very expensive in a cost-per-person basis at the rates that we as a society use water.  In the context of a multibillion dollar navy vessel where cost is not an issue and where water efficiency rules are enforced, it is much less problematic.  


In short, it really isn't that expensive, it's just that we waste huge amounts of water in ways that we clearly wouldn't if we had to pay for desalination of all the water we used.  If we drastically changed our lifestyles to conserve water the expense to keep ourselves alive would be much more reasonable.