A 12V watermaker can run entirely on solar power, without a generator. The LEDI Scout draws 16 to 18 amps at 12V, which a standard house battery bank topped up by 200 to 400 watts of solar handles comfortably. This guide covers exactly what you need to run a watermaker on solar, what the numbers actually look like in practice, and where the limits are.
Why solar and 12V watermakers are a natural match
Most cruising yachts and off-grid setups already have a 12V house bank. Adding a watermaker to that system is straightforward if you understand the amp draw. The Scout runs at 16 to 18A at 12V, which is roughly the same load as a modest 12V fridge running hard. You are not asking the system to do anything unusual. The key advantage over a 240V or high-draw system is that you can top up the bank between sessions with solar alone, no shore power or generator required.
How much solar do you actually need?
The answer depends on how many litres you need per day and how much sun you have. Here is a practical baseline:
- Scout 10 LPH: produces 10 litres per hour at 16 to 18A draw. To make 40 litres a day, you run it for 4 hours, using roughly 70 amp-hours (Ah) from your bank.
- Scout 20 LPH: produces 20 litres per hour at the same 16 to 18A draw. 40 litres takes 2 hours, around 35 Ah.
- 200 to 400W of solar in good tropical or subtropical sun produces roughly 40 to 80 Ah per day depending on angle, shade and hours of usable light.
In practical terms, 200W of solar covers a Scout 20 session for daily drinking and cooking water with margin left over for navigation electronics and lighting. A 400W array gives you more buffer for overcast days and higher consumption. These are ballpark figures; your actual yield depends on your location and panel placement.
What battery bank do you need?
Running the Scout directly from the battery bank while solar is charging is fine. The unit does not require a dedicated circuit, just a clean 12V supply rated for at least 20A continuous. A 100Ah AGM or lithium battery can run a Scout 20 session of two hours without difficulty. Lithium (LiFePO4) banks are particularly well suited because they tolerate deeper discharge and charge faster from solar, but AGM works well if you keep an eye on state of charge. The rule of thumb is: do not run the watermaker below 50% state of charge on an AGM bank, and plan your sessions for when solar input is highest.
Can you run a watermaker while sailing in low wind?
Yes. Many sailors run the Scout during a passage when the engine is charging the bank, or during sunny daylight hours when solar keeps up with demand. Because the Scout is portable and needs no permanent wiring, you can also time sessions to suit your power budget rather than running it continuously. The built-in hour meter helps you track usage and plan maintenance without guessing.
The Nomad on solar: a bigger ask but still achievable
The LEDI Nomad, producing 40, 60 or 80 LPH, draws more power and suits larger vessels with a bigger bank. At 12V or 24V DC, it is still solar-compatible, but you will want a well-sized bank and a larger array. For charter boats, liveaboards and bigger crews where daily water demand is high, a 24V system with 600W or more of solar is a realistic target. Contact the LEDI team to discuss the right configuration for your setup.
Practical tips for solar-powered watermaker sessions
- Run the watermaker during peak solar hours (roughly 10 am to 3 pm) to minimise net draw on the bank.
- Check battery voltage before starting; a healthy 12V bank at rest reads around 12.6 to 12.8V.
- Keep the pre-filter clean. A blocked 5 micron pre-filter increases head pressure and can reduce output, making each session less efficient.
- After each session, flush the membrane with fresh water. This protects the membrane and means your next session starts clean. The Watermaker Install Kit includes the fittings to make this easy.
- Track your running hours using the built-in hour meter so you know when to service the system.
Solar watermakers vs generator-powered units: honest trade-offs
A generator gives you unlimited power on demand, but it burns fuel, creates noise (the Scout runs at around 65 dB, about the same as a dishwasher), and adds a maintenance item to the boat. Solar adds no fuel cost after installation and suits boats already carrying panels. The Scout's 12V design was built with solar-first operation in mind. The trade-off is that output per session is limited by your bank and solar capacity, so planning matters more. For a two-person crew making 40 to 60 litres a day, a well-sized solar setup handles this without stress.
For more detail on how 12V watermakers fit small yachts, read 12V Watermakers for Small Yachts and Sail Further on Solar. If you want to understand how much power a watermaker actually uses day to day, Can a Watermaker Run on Battery Power? goes deeper on the numbers.
Frequently asked questions
How many watts of solar do I need to run a 12V watermaker?
200 to 400 watts of solar is a practical range for daily use with the LEDI Scout. At 200W you can cover a two to four hour session on the Scout 20 during peak sun, producing 40 to 80 litres, with enough margin left for other boat electrics. More panels give you more buffer on cloudy days and in higher latitudes.
Can the LEDI Scout run directly from solar panels without a battery?
No. The Scout needs a stable 12V DC supply, which solar panels alone cannot provide reliably (output varies with cloud and angle). Always run it from a battery bank that solar is charging. The battery acts as a buffer and ensures steady voltage to the pump.
Does the Scout work with lithium batteries?
Yes. The Scout accepts any stable 12V DC supply, including lithium (LiFePO4) banks. Lithium is well suited to watermaker use because it charges faster from solar, tolerates deeper discharge and maintains voltage more consistently than AGM across its discharge range.
Will running a watermaker flatten my battery bank?
It depends on your bank size and session length. A 100Ah bank running a Scout 20 for two hours uses roughly 35 Ah, leaving 65 Ah available, well above the 50% recommended minimum for AGM. With solar replenishing the bank during or after the session, net draw is often minimal. Size your bank and panels to your daily water target and you will have no issues.
Ready to run fresh water on solar? The Scout starts from $4,899 AUD and needs no installation. Browse the Scout range or get in touch with the LEDI team at info@ledi.com.au or +61 494 562 668 to talk through your power setup before you buy.
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