“This was far cheaper than I’d have guessed, and in a water crisis I would agree that this is “absurdly cheap”.”
Reverse osmosis takes about 3.5 kWh per cubic metre, and a year of drinking water for one person costs $2.30. Desalinated drinking water for all 8 billion people would add 0.1% to world electricity demand. The WHO minimum of 50 litres a day would take 64 kWh per person, which is what the average Malawian uses for everything. The water was never the expensive part. The poverty is.