How many amps does a watermaker draw?
It depends entirely on the voltage, because amps are just watts divided by volts. The 18 DC systems we rank draw from 9 to 104 amps at 12 V, and half that at 24 V for the same work.
Running current is the number that sizes your cable and your breaker. Amp-hours a day is the number that sizes your battery bank, and the two can point in opposite directions: a system pulling 104 A for twenty minutes is easier on a bank than one pulling a third of that for two hours.
Doubling the voltage halves the current for the same power, which is why bigger boats go to 24 or 48 volts — not because it makes the watermaker more efficient. Watt-hours per litre does not change with voltage at all.
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.