Watermakers for solar-powered boats
This is the sharpest version of the whole problem. With no generator, every litre comes out of the array, and the difference between systems is the difference between filling the tanks and watching the bank sag.
The power reality. A 400 W panel yields roughly 1,600 Wh on a clear Queensland day, and the fridge is taking a large share before the watermaker sees anything.
What matters on solar-powered boats
Only the low band really works
At 3.7 Wh/L, 100 litres costs about 370 Wh. At 19.7 Wh/L the same water costs nearly 2,000 Wh, which is not a solar proposition.
Time the run to the sun
Running mid-morning to mid-afternoon uses generation directly and avoids the round-trip losses of the battery.
Cloudy weeks are the design case
Size tankage so you can skip two or three poor days rather than oversizing the watermaker for them.
The premium is often the cheaper path
The extra panels and battery a thirsty system needs frequently cost more than the efficient unit you did not buy, and they weigh more.
Shortlist for solar-powered boats
The 8 best matches of 16 that suit solar-powered boats, ordered by energy per litre. Run time and energy below are for 66 litres a day.
| System | Power | Output L/hr | Draw W | Wh per litre | Price |
|---|---|---|---|---|---|
| Zen 30 Schenker | 12/24V DC | 30 | 110 | 3.7 | $6,300 |
| Zen 100 Schenker | 12/24/48V DC or AC | 100 | 400 | 4.0 | $9,600 |
| Ventura 150 Deluxe Spectra | 12/24V DC | 24 | 108 | 4.5 | $6,000 |
| Ventura 150 Connect Spectra | 12/24V DC | 24 | 108 | 4.5 | $7,400 |
| Newport 400C Spectra | 12/24/48V DC | 64 | 288 | 4.5 | $14,500 |
| Zen 50 Schenker | 12/24V DC | 50 | 240 | 4.8 | $7,800 |
| D100 DUO Dessalatorreported | 12/24V DC | 100 | 700 | 7.0 | on request |
| D60 Freedom Dessalatorreported | 12/24V DC | 60 | 550 | 9.2 | on request |
Common questions
- Can you run a watermaker on solar power alone?
- Yes, with an energy-recovery DC system. The most efficient in our table makes 100 litres for about 370 Wh, which one 400 W panel covers on a clear day.
- How much solar do I need for a watermaker?
- Work backwards: daily litres multiplied by the system's Wh per litre gives the energy needed. For 100 litres from an efficient system, one 400 W panel's surplus is enough. For a thirsty system you would need several panels dedicated to water.
- Should I run the watermaker during the day or at night?
- During the day, straight off generation. Charging the battery and discharging it again wastes energy you cannot spare, and it leaves the bank intact for the night.
Guides that go deeper
Not quite your boat?
How the shortlist is built. 66 litres a day is 3 aboard at 22 litres each — a planning figure for this kind of boat, not a measurement of yours. The list is filtered to systems whose power source suits solar-powered boats and ordered by energy per litre. Every figure is the manufacturer’s rated output and draw; Wh per litre is one divided by the other. Methodology.