How many litres per hour do I need from a watermaker?
Divide your daily need by the hours you actually want to run it. For a crew of 4 needing 100 litres and a comfortable one-to-two-hour run, that is 50–100 litres an hour — which is the middle of the market, not the top of it.
The window matters more than the number. If your power comes from an engine that runs an hour a day anyway, buy output and fill the tank inside that hour. If it comes from panels, a slower system running through the middle of the day is easier on everything and usually far cheaper per litre.
Buying more litres per hour than you can power is the common mistake. Output is cheap to specify and expensive to run — check what the hours cost in watt-hours before you decide the size.
Where this is worked through
Other quick answers
Where these numbers come from. Every figure on this page is computed at build time from the comparison table — rated output and rated draw as the manufacturer publishes them, with watt-hours per litre derived as one divided by the other. Nothing is typed in by hand, so nothing here can drift from the table. Where a figure is an assumption rather than a specification it is labelled as one. Methodology · the table.