How many watts does a marine watermaker use?
Between 108 W and 2,800 W across the 30 systems we rank, with a median of 1,250 W. Watts on their own tell you almost nothing useful, though — a big pump that runs for twenty minutes can cost less energy than a small one running for three hours.
The figure that decides what a watermaker costs your batteries is watt-hours per litre: the draw divided by the output. Across the same systems that runs from 3.7 to 19.7 Wh/L — a factor of 5.4, far wider than the spread in wattage.
Put concretely: 100 litres a day costs 367 Wh on the Schenker Zen 30 and 1,969 Wh on the Rainman Modular AC 70L. Both are perfectly good machines; they are answering different questions.
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.