All Hands on JOOOL Hybrid Electric Propulsion

Published: Thursday, November 27, 2025 9:00 am
By: Zuzana Prochazka

A week of experience with an alternative propulsion system.

I’ve tested many electric and diesel-electric propulsion systems over the past few years, but it’s one thing to drive one for an hour and another to live with one for a week in a real-world application. That’s why I jumped at the chance to charter a Dufour 53 sailboat from Dream Yacht Charter that was equipped with the JOOOL system (yes, three “Os”), a hybrid solution with a large battery pack and a diesel genset range extender.

Our cruising grounds were the Aeolian Islands off the northeastern tip of Sicily. The islands of Panarea, Stromboli, Lipari and so forth are all line-of-sight on the horizon and we covered about 100 miles that week. We had painfully little wind so we put the system through its paces as we motored all but one day.

What is the JOOOL System?

The system was designed by Alternative Energies and is now marketed under the brand JOOOL. It’s electric propulsion and is available for sailing monohulls and catamarans 35-65 feet.

The system is built around four elements that manage energy flow for propulsion as well as house needs including refrigeration, lighting, air conditioning, and so forth. The first component is the PowerPOD appendage that resembles a Saildrive below the hull. It’s sized at 25kW, 35kW and 50kW depending on the boat.

Next is the heart of the system called OneBox. This resides where the typical diesel engine would be and it was strange to lift the companionway stairs and see only that box rather than an engine. It’s the source of energy management and conversion, as it integrates all energy inputs and outputs including solar, hydrogeneration, generator, and shore power.

Next up is the EPMS or the brain of the system that communicates with the OneBox and optimizes energy flows. Finally, a large bank of lithium iron phosphate batteries is the muscle that allows you to run most of the ship’s systems quietly for extended periods at anchor. The batteries supply 12/24VDC for accessories like electronics and lighting, and 160-496VC for propulsion. There’s also support for 230VAC. High DC voltages reduce the electrical current needed to drive the motor. A fire suppression system activates at 80 degrees Celsius for safety, and a two-year warranty covers the system while the batteries are warranted for eight years.

The components are connected to a diesel genset which functions as a range extender. The genset is programmed to kick on when the batteries reach 40% capacity and that happens automatically. On shore power with the standard sized charger, the system will charge from 10-40% in four hours or about half that time with the upgraded 6kW charger. As a bonus this system doesn’t require heavy duty wiring or water cooling, which altogether reduces maintenance needs.

Our Dufour 53 was outfitted with a 35kW pod, a 38kWh battery bank, and a 13kW genset. Four solar panels (unknown wattage) were sewn into the canvas Bimini top. Larger solar arrays like those on catamarans would do better than ours that only registered about 200 watts of incoming power.

What Were the Results?

For the first two days, I was glued to the screen keeping tabs on performance and I found the results to be consistent. We motored at 6 knots at 800 rpm drawing 12kW on flat water since there was no wind, barely any current and very little chop. We motored for two hours before the battery bank reached 40% and the genset turned on automatically. The only confusion came when the batteries were topped up and the genset kept running for a few minutes as it cooled down, but we soon got used to that.

We didn’t experience the hydro-regeneration feature that feeds power back into the batteries with the propeller spinning when the boat is sailing. Our top speed under sail was 6.5 knots and that was only for a short time. Presumably, the regen element should start around 5 knots but for us, the propeller locked in that mode but didn’t produce discernible power. The 40% setting on the genset start is changeable but was programmed that way for charter skippers to ensure the batteries remain charged and protected.

The JOOOL system performed without any user intervention and for that, I was grateful. It functioned as designed and stayed consistent in performance throughout the week. Because the genset as well as the pod were situated below the cockpit sole on our monohull, both were audible with the genset of course generating more sound and vibration than the electric motor. A catamaran installation may be more suitable because there’s better separation between the living spaces and the machinery so it would be less noticeable. Also, with more room to install a larger solar array and a bigger battery bank, a multihull is a more amenable platform.

What’s the Best Application?

Perhaps the best application for this system is where JOOOL already has its installed critical mass and that’s in successful commercial applications like commuting ferries and water taxis. There, the use case is different from a cruising sailboat and includes short distances with plenty of charging time at frequent docks stops.

The Verdict

My overall verdict is positive and I can say my worries about not being an electrician were for naught. It’s a foolproof system that allows the user to stay only as involved as they want to be because everything functions without the need for supervision. It was a flawless hands-on experience and how often can you say that about anything while cruising?

tags: BoatTest, Dream Yacht Charter, Dufour 53, JOOOL, sailboat, Sailing, sailing community