MULTIpedia #08 - 2025.07.29

THE 100% MULTIHULL NEWSLETTER

Jul 29, 2025

HYBRID PROPULSION: “WATT’s” NEW?

While sailing boats are hybrid by nature, hybrid propulsion offers further advantages for reducing their carbon footprint without sacrificing comfort or autonomy. However, there is still considerable reluctance towards fully electric propulsion, particularly for long-distance voyages as there is a long way to go between promise and reality. So we took stock with four players who shared their vision of this transition, which could gradually transform the use of multihulls.

The idea of combining electric motors and thermal generator(s) is not new, we particularly remember the Lagoon 420 hybrid in 2006. But it is reaching a new milestone thanks to lithium battery packs that are both more efficient and more affordable, and to smarter systems that are better integrated and adapted to the specific needs of multihulls. For Tom Pickles of Integrel Solutions, their system starts with an intuition: "The idea is to use the excess energy that you have, as the engine is always producing more energy than the prop curve needs, so we take some of that energy and convert it using E-Power into lithium battery storage. An E-Power 9 (9kW) managed by a software system is almost double the amount of power you can get out of any output alternator." In five years, their E-Power system, which transforms the main engine into a high-power generator, has already been installed in more than 500 units. Already winners of a Dame Award, they are back in 2023 with the E-Drive, an even more ambitious project that combines energy production with electric propulsion. An electric motor is installed on the shaft line or saildrive, allowing the boat to move in all-electric mode. When not used for propulsion, the same system acts as a generator. In combustion engine mode, it recovers mechanical energy from the engine to produce electricity and recharge the on-board lithium batteries. This eliminates the need for a generator. The system therefore allows the boat to sail in 100% electric mode, then switch to combustion engine when power or range requires it. This is an interesting technical approach for cruising multihulls, and its modularity is attracting more and more shipyards. "We work with a dozen OEMs globally. Balance Catamarans is a very key OEM that we work with. There hasn't been a Balance catamaran with a diesel generator on it for four years" confirms Tom.

At Excess, the approach is even more pragmatic, as Hervé Piveteau, their product manager explains: "We built an Excess 15 Hybrid in 2022, which was quite promising in terms of technology, clearly demonstrating the advantages of hybrid technology, but also its limitations in terms of cost. We launched a survey on the speed-range-price equation to find out what was acceptable from a customer perspective, and we couldn't tick all three boxes at the same time. In short, if we wanted to meet the objectives in terms of range and speed, we couldn't tick the price box. So we put the subject on hold”. But, with the Island Cruising Concept prototype, the Bénéteau group hopes to strike this delicate balance. The design office of the group's youngest brand immediately set to work and the result was positive: "the layout could be adapted to the Excess 11 and, for the first time, we felt we had a complete system that fit within an acceptable budget for the customer."

Keeping It Simple

Whether they are manufacturers, equipment suppliers or sailors, everyone is looking for simplicity. Integrel opted for 48 V, which Tom Pickle believes is "one of the things that made E-Power so successful. It allows us to push a very large amount of current into battery banks very quickly. It's also considered safe. But yachts sail around the world, and we need systems on our boats that electricians can work on safely anywhere in the world without needing a master's degree in technology." To keep things simple, the E-Drive system is air-cooled and can be fitted to engines from 40 to 150 hp, on both propeller shafts and saildrives, regardless of brand. A dozen multihulls have already been fitted, including a Balance 526, about which Tom Pickle reveals an interesting equation: "You can run at about 5 to 5.5 knots for 5 hours on a 30kW battery bank, and then turn on your diesel engine and recharge that battery bank in one hour. So you can do 5 hours of electric propulsion and then recharge for one hour while you are still moving, so you only use one hour of diesel for every six hours of motoring". However, these figures should be taken with care as they always depend on sea conditions, wind strength and direction.

It is important to note at this stage that there is no universal solution; you have to work with the boat's DNA, its size and its programme. At Excess, the choice fell on Fischer Panda engines of 10 kW each, "immersed pods, which provide the best possible efficiency and direct cooling" explains Hervé Piveteau. Each engine is connected to a dedicated battery bank nearby, "all in 48V, so there is no loss due to conversion. These battery banks are charged by a single DC generator. We have therefore made significant progress in reducing the line losses that this type of system can have," reassures Hervé Piveteau, adding, "in terms of performance, we achieve the same cruising speed, slightly less in terms of top speed, but we are better in terms of torque, which is good for manoeuvring in port. We also have better speed maintenance in rough seas, and that's a real innovation. We have a range close to that of the thermal version, bearing in mind that we have kept the same tanks."

The Delos Approach

For Brian and Karin Trautman, the hybrid project by SV Delos (see MULTIpedia #07) is more original: "We opted for an asymmetrical diesel-electric mix. On one side, there is an 80 hp engine coupled with a 25 kW electric motor, and on the other, just a 25 kW electric motor." This gives them the safety of a mechanical drive but also allows them to navigate in full electric mode if they . Having only one combustion engine on board means less weight (250 to 280 kg for a combustion engine between 50 and 80 hp fully equipped), less maintenance, and it's quite pragmatic: "it's very rare that we run both engines, for fuel efficiency. If we really need a lot of power, to get out of a passage, or go straight upwind into the waves and 20 knots, we'll need the second engine, but generally you run on one and alternate them to keep the hours the same." And when we mention the safety provided by having two combustion engines, Brian points out that on their monohull they only had one engine "for almost 90,000 NM and I never wanted a second one because you have two to maintain, two to pay for".

Unlike the E-Drive and Excess systems at this stage, the installation planned in cooperation with Nanni incorporates hydro-regeneration, which is interesting for long distances. Brian adds that they can also "disconnect the propeller shaft from the diesel engine side and run the diesel engine coupled to the two electric motors as a giant alternator, which is the equivalent of a 20 kW alternator. We will have quite a few lithium batteries, about 54 kWh, which, under pure electric power, if our figures are correct, should give us a range of 30 to 40 NM. It's not a huge range, which is why we have the diesel engine that will give us well over a thousand nautical miles." The design imagined by Brian is interesting, even if it has yet to be validated in practice, but that doesn't scare him: "Because we are building this boat for ourselves, we have the ability to try some interesting things, and if it doesn't work, we will revamp and re-engineer it. It's more like an evolution of the project, which, as an engineer myself, I really like!"

Industry Moves In

In contrast to this empirical version of S/V Delos for personal use, the Fountaine-Pajot group has developed, through its subsidiary Alternatives Energies acquired in 2022 and the Joool brand, an industrial solution that aims to meet its ambition of carbon neutrality by 2030. It is their system that can be found in the ODSea+ version of the NEW 41 and 44, which will be unveiled at the next Cannes Yachting Festival. Although we have not yet been able to test sail them, we did sail on the Dufour 48 ODSea+ equipped with the same system but with a single 25 kW engine instead of two. Romain Lucas, their Design Office Manager, explains how it works while we are at sea: "It's a hybrid engine, which means that we have a generator that starts automatically as soon as you reach 40% battery power. We left the dock at 100% and were down to 85% outside the harbour after hoisting the sails." The user interface, with a screen displaying only two pages, is particularly simple, and the skipper can choose between three modes:

- Propulsion: the synoptic display clearly shows the flow of energy from the 27 kWh lithium battery bank to the 25 kW 400 V electric motor. The revolutions per minute and watts consumed are also displayed.

- Neutral: in light winds, engine off, no hydro-generation.

- Progressive hydro-generation: on the screen, the direction of the energy flow is reversed to go from the propeller to the battery bank. The throttle is then used like the engine brake of an electric car. The more you push the throttle, the greater the electrical production, but also the greater the hydrodynamic braking. This is an interesting modulation because it allows you to adapt to wind conditions. Electricity is generated gently in the medium, before charging to maximum when the breeze picks up and the boat is at full speed.

Currently equipped with a specific fixed three-bladed propeller with a diameter of 50 cm (19.68 Inches) – a version with folding blades is being studied – the loss of speed remains quite acceptable. In 16 knots of wind, sailing at 7 knots, we lost 0.3 knots to produce 1 kWh, then 0.5 knots with the "engine brake" fully engaged, producing up to 2 kWh. We left the dock with the batteries fully charged, as the boat had been connected to shore power throughout the Palma boat show. With the 6 KVA/30A charger, one night connected to a 30A shore power outlet allows the batteries to go from 20% to 80% charge. Better still, with hydro-generation, we had more energy in the batteries when we lowered the sails after just one morning of testing than we had when we hoisted them once we left the port under engine power. And that was without the help of the 14 KVA generator integrated into the ODsea+ pack, which would have started automatically if the battery level had dropped too low. But on that sunny spring day, with 1100 Watts of solar panels on the rigid hardtop, we didn't need a single drop of fossil fuel.

Alternatives Energies recorded the following measurements on a Leopard 46 (which shares the same Joool technology as the future New 44 from Fountaine Pajot) for two 25 kW electric motors equipped with two 27 kW battery banks and a 12 kW 220 V AC inverter:
- in full electric mode, the range would be 8 hours at 4.5 knots and 4 hours at 6 knots.
- in hybrid mode, the range would be 920 NM at 6 knots and 550 NM at 7 knots.
- 1 hour of charging with the generator (45% of battery charge) should provide between 2 hours of electric motor at 6 knots or 4 hours at 4.5 knots, or autonomy for an entire day of mooring, with 12 hours of air conditioning,
- Motoring genset on would give you 7.5 knots cruising speed.

Still a Long Way to Go

From their different perspectives, they all share the same conclusion: hybrids will not replace diesel overnight. Especially since, although the price tag is getting lower, it is still substantial: from USD55,000 for a Dual E-DRIVE Integrel 15 KW to €200,000 for a complete installation on a 45-to-50-footer all included (electrical engines, battery banks, inverters, solar panels…). These figures should always be put into perspective according to the power of the engines installed, the power of the battery banks, solar panels, chargers, and converters. But in addition to the revolution it offers in terms of silent sailing, the hybrid system is transforming the way energy is managed on board in a reliable manner. Tom Pickle states that "the engine manufacturer's warranty is not affected by having our product attached to it" and that in five years of existence, no incidents have been reported.

From prototype to production boat, from passionate DIY enthusiasts to industrial manufacturers, the transition to hybrid is taking shape through compromise and iteration. While the cost-speed-range equation remains delicate, solutions are becoming clearer, feedback from the field is refining choices, and the first sailors are confirming the essential: yes, hybrids are changing life on board. It remains to be seen how many more miles will be needed for this dream of gentle propulsion to become the norm for the majority — without sacrificing any of the freedom that makes sailing so special.

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SPOTTED

Two in a row! After 2023, Tom Laperche once again crossed the finish line first in his second Rolex Fastnet Race aboard the trimaran SVR-Lazartigue. As dawn was showing its first rays this morning off Cherbourg-en-Cotentin, so the sleek light blue triple-hulled form sped across the finish line of the 51st Rolex Fastnet Race to collect overall line honors after 1 day 17 hours 18 minutes 4 seconds at sea. A 100%-win rate in the race marking the centenary of both the event and its organiser, the RORC, makes perfect sense.

IN SHORT

51%

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EPIC

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SOMEDAY

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YETI

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Cannes premiere

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Orange light

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Deal

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People

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MEDIA CENTRE

Opening of SailGP Technologies in Southampton / Sails (EN)
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