A low power watermaker on a sailboat comes down to one number, the watt-hours it takes to make a litre. Two new units are in the show reports this season and both are sold on that number. The Cruiser Services CS-40 is listed for the Annapolis Sailboat Show, which runs from 15 to 18 October 2026. Dessalator's brushless D60 and D100 were at Southampton in September. We were not at Southampton and we are not going to Annapolis. We are on a Fusion 40 in Fiji and we have not tested either unit. The figures come from the show listings and the makers' own pages, and the sums are ours.
Watt-hours a litre is the number to compare
Litres an hour tells you how long you run it. Watts tells you what it pulls while it runs. Divide the watts by the litres an hour and you have watt-hours a litre, which is what the water costs the battery bank. A unit that makes 100 litres an hour on 450 W uses 4.5 Wh a litre.
The Yachting Monthly watermaker guide puts energy recovery units at 4 to 5 Wh a litre and says high-pressure units need between two and three times that. It also says a high-pressure pump can draw upwards of 500 W, and that an energy recovery unit can be run on 12 V with as little as 9 A. That guide is from 2023. Both units below are high-pressure pump designs and both claim to do better than that, which is why they are worth a look.
The CS-40 makes a lot of water on a small AC supply
The SpinSheet new products list for Annapolis has the CS-40 at 33 to 40 US gallons an hour on under eight amps at 120 V AC. That is 125 to 151 litres an hour. It has a stainless steel head piston pump and automatic flushing, and it measures the product water and diverts it without you. The Annapolis show listing puts it in Tent D, stands 33 and 35.
Now the sums. Eight amps at 120 V is 960 W at the most. At 151 litres an hour that is about 6.4 Wh a litre, and at 125 litres an hour it is about 7.7. The listing says under eight amps, so the real figure should be lower. We don't know by how much.
The Cruiser Services CS-40 page lists the dual membrane system at USD 5,495 with a 1 hp drive motor, and a CS-40-DC at USD 5,595 described as 12 V and 80 amps. Twelve volts at 80 amps is also 960 W. The company claims a four year warranty and has an office in La Paz, Mexico. It is also the Schenker distributor for the United States and Mexico, so it sells energy recovery units next to its own.
This is a unit for a boat that wants a lot of water from a short run. On AC it goes through the inverter. On DC, 80 amps at 12 V is heavy cable and a big breaker.
Dessalator went brushless on the D60 and D100
Dessalator's updated Freedom and Duo units had their UK premiere at Southampton. The Southampton gear report in Yachting Monthly gives them brushless DC motors, 60 and 100 litres an hour from the D60 and D100, and 450 W on the D100. It says the motors stay cool in ambient temperatures up to 50°C and run on lead-acid or lithium banks. A brushless motor has no brushes to wear out.
450 W for 100 litres is 4.5 Wh a litre. If the number holds, that is an energy recovery figure from a pump with no energy recovery unit in it. The Dessalator Duo specifications still list 370 W for the Duo 60 and 600 W for the Duo 100 on DC, which works out at about 6 Wh a litre for both. That may be the earlier brushed model. We don't know, and we said the same in our Southampton gear round-up. Get the draw at your system voltage in writing before you order.
The UK distributor lists a D60 Freedom at £8,695 before VAT and 38 kg. We don't know if that listing is the brushless version, and we have not seen a price for the brushless D100.
Energy recovery units still set the mark
An energy recovery unit runs a small low-pressure pump and takes the pressure back out of the brine to help drive the feed water. Spectra says its Newport 400C watermaker operates on as little as 15 watts per US gallon, which is about 4 Wh a litre. The Yachting Monthly guide's caution is that these units are more complex and cost more.
On paper the gap has closed. A claimed 4.5 Wh a litre from the D100 against about 4 from an energy recovery unit is close enough that the choice comes back to output, spares and who can fix it where you cruise.
What a cat with 700 W of solar can run
Mā Tori has 700 W of solar, a 540 Ah lithium bank, a 2000 W inverter and an OceanF10 watermaker fitted in 2025. The rest of her systems are in the Fusion 40 review.
We have not published the litres an hour or the amp draw of our own unit, so we are not quoting a figure for it here.
What we can do is put the two new units against those numbers.
- The D100 at the reported 450 W sits inside what a 700 W array can make in full sun. An hour of it is 450 Wh for 100 litres.
- The CS-40 on AC, at up to 960 W, is inside the rating of a 2000 W inverter. It is more than a 700 W array makes at its best, so the bank covers the difference and the panels put it back afterwards. An hour of it is up to 960 Wh for 125 to 151 litres.
- The CS-40-DC needs 80 amps at 12 V. Measure the cable run from the batteries to where the unit would go before you choose the DC version.
700 W is the panel rating. What an array makes over a day depends on cloud, latitude and shade from the boom, and we are not putting a number on ours. Panel area is the limit on all of this, which is the point we made about the Solar Explorer version in the Knysna 550 preview.
What we would check before buying
- The draw at your system voltage, in writing. The two published figures for the D100 are 150 W apart.
- Start-up surge. A motor pulls more when it starts than when it runs, and neither listing gives that figure. Ask for it and compare it with the surge rating of your inverter.
- Spares. Cruiser Services has its office in Mexico and Dessalator is French. We don't know who carries membranes, pump seals and pre-filters for either between Fiji and New Zealand.
- Weight. The D60 Freedom is listed at 38 kg. We could not find a weight for the CS-40.
- Membrane care. The Yachting Monthly guide says a membrane can sit for around five days before growth becomes a risk, should be flushed with fresh unchlorinated water if it is idle for longer, and should be pickled if it will sit for more than a month. Automatic flushing takes care of the first part of that.
- Where you run it. The same guide says to avoid making water in anchorages where other boats are not using holding tanks, because the pre-filters collect what the membrane stops.
What we don't know
- How either unit performs. We have not seen or tested one.
- Whether the 450 W reported for the D100 is at 12 V or 24 V.
- How far under eight amps the CS-40 runs.
- Australian and New Zealand prices and stockists. The prices here are in US dollars and pounds, from the sources linked, as published in early October 2026.
Prices and specifications change, so check the maker's current page before you order. A new inverter load or an 80 amp DC circuit is electrical work. Check the current official electrical standard for your flag, and what your insurer requires, before it is wired in.
Questions people ask about low power watermakers
How much power does a watermaker use on a sailboat?
Yachting Monthly puts energy recovery units at 4 to 5 Wh a litre and high-pressure units at between two and three times that. The two new high-pressure units here work out at 4.5 to about 7.7 Wh a litre on their published figures.
Can a watermaker run from solar and lithium?
Yes, if the draw fits your inverter or DC wiring and the array can put the energy back. A 450 W unit sits inside the full sun output of a 700 W array. A 960 W unit does not, so the bank covers the difference.
How much water does the Cruiser Services CS-40 make?
The show listing gives 33 to 40 US gallons an hour, which is 125 to 151 litres, on under eight amps at 120 V AC.
How long can a watermaker sit unused?
Yachting Monthly's guide says around five days before growth on the membrane becomes a risk. Flush with fresh unchlorinated water if it will be longer, and pickle it for more than a month. Check the maker's manual for your unit.
Has the crew of Mā Tori tested these watermakers?
No. We were not at either show and have not tested either unit.
Keep reading: what to look at on a boat's systems before you pay is in the Catamaran Buyer's Pack, why the fit-out matters more than the badge is in the owner-built against production guide, and our bluewater catamaran for sale is the boat this was written from.