Electric Catamarans: Is Carbon-Free Safe & Successful?

Electric Catamarans

When thinking about electric catamarans over the years, I have often wondered how green a sailor can be without compromising safety and requisite redundancy on a cruising catamaran.

Sailboats are by their very nature already green or relatively low-carbon since the primary source of propulsion is wind.

Having done extended cruising and ocean crossings over the last 28 years, we have encountered most situations that seaman come across. While, luckily and surely, we have not seen it all, weather, equipment and system failures, human error, and other perils like pirates have thrown down gauntlets along our adventures. In almost all of these challenges, having access to ready sources of energy whether it be fossil fuel engines or other greener sources of power was the key to the safety of our boat and our crew. Certainly, an  energy management plan aboard is prudent, safe, and affordable but also a step in the right direction for our planet’s health. (We are huge fans of Silent Yachts and follow their progress with bated breath).

But is a carbon-free catamaran safe? Can it take us successfully through an average extended cruising scenario?


siyaya, a catamaran, during stephen and estelle cockcroft's atlantic crossing in 2006
We were involved in the construction of the first electric Island Spirit built in Cape Town, South Africa, in 2003. She was fitted with the Solomon Technology electric-wheel motors. It was at this point where I realized that while there were many benefits and I really liked the idea of electric propulsion, there were definitely shortcomings.

From a practical standpoint I do not like giving up options and redundancy when doing extended cruising. For me this is a safety issue. The creature comforts like refrigerated food storage for fresh food over weeks, hot meals, and warm showers are hard to give up.

But, in the past 2 decades, advancements in electricity generation aboard vessels has made impressive strides. As I never quit thinking about electric catamarans, when we recently completed crossing the Atlantic as part of the ARC Rally, we decided on an energy management plan that incorporated multiple system solutions instead of reliance on one main energy or battery-charging source.

Our power solutions for the ARC Rally and for future years of living aboard our Bali 5.4 include:

  • Solar – the factory installation is 850 watts, we increased this to 1,200 watts
  • Watt & Sea hydro-generator – since our energy plan utilized multiple energy generation solutions, we opted for the 300 model instead of the 600. I am not a fan of regenerating power through the main drives because of all the moving parts. We chose the Watt & Sea hydro-generator as it is much more efficient and super reliable with less drag.
  • Large additional alternator – 125 amp on each engine to maximize charge when running the engines
  • We opted for a smaller diesel generator, of 13.5 KW rather than the standard 21 KW offered by the factory. And we have a 3 KW inverter charger that gives about 80 amps charging capacity
  • The last piece of our energy generation puzzle will be to replace our current AGM batteries at the end of useful life with 1200 A/H of lithium-Ion batteries. Craig at Maz Ocean install lithium batteries on catamarans and are experts in this arena. Their team will likely recommend and install Lithionics or Victron Li-ion batteries. 

We tested our  multi-source energy management plan for our catamaran as we sailed 3,060 NM from the Canaries to St. Lucia. Total fuel consumed was 46 gallons. Averaging it out, we used less than 2 fluid ounces of fuel per Nautical Mile which I think one could certainly consider very green.

The power consumption for the boat with all the electronics going, the watermaker keeping tanks topped off for crew use, all the fridges cooling while running off inverters (keep in mind Bali’s American-sized fridge!), and the galley in full swing with microwave, panini maker, coffee pot, and more to perpetually feed our crew of 8, the average hourly draw was 35 amps.

During the day when the solar and hydro-generator were topping up the batteries with power, we had a positive input of around 7 to 8 amps. At night when the solar went dark, we had the navigation system and interior lights which created a shortfall of around 12 to 15 amps.

The big meal of the day was early evening dinner when the galley would have all sorts of appliances going. So, consequently, we ran the diesel generator for one to two hours during that point of high use by the crew. During this time, the batteries charged up for the night and we made water to keep the tanks topped off and heated the water for showers. Since we were not motoring for most of the trip, the engines were not heating the water.

When we planned this voyage, we decided that we would not be that boat that had to camp, be conservative, or rough-it in any way. We have done this enough over 20+ year sailing career. The Bali 5.4 is a large comfortable catamaran and we kept it that way ensuring our crew could use water at will to shower, drink, cook, and clean. The fridge is a double-door stand-up fridge/freezer which has its own dedicated inverter and was full of food. Also, a flybridge fridge for drinks was in operation.

The take-away from this 16-day trip with eight crew on board is that the power generation and management worked well. We proved it could function providing a safe and comfortable voyage for an extended period.

When just Estelle and I are cruising, we have a much smaller power consumption requirement even with keeping our favorite creature comforts. We love to sail and, whenever possible, the engines are shut down and under sail even if it is a slow trip. But at below 4 knots, I run one engine to keep way on so the autopilot does not have a hissy fit. So, this energy management plan that most would call low-carbon or green sailing is working beautifully for us until the next great ideas reduce my concerns of current green energy generation and storage methods to make a truly carbon-free electric catamaran possi

Electric-Powered Catamaran Concerns

Here are my concerns with the trend to all-electric sailing based on experience and what I have witnessed over the years.

Loss of Redundancy Imperils Safety

  • Two diesel engines and sails give you 3 forms of propulsion, all the redundancy you need to maintain safety:
    • Both engines working.
    • If one engine goes out, there is a backup.
    • If both engines go out, you still have the sails.
  • On an all-electric boat with a generator, you have only two reliable sources of propulsion:
    • Electric propulsion from a generator as the batteries must be charged because the batteries will only give you a short period of propulsion until the generator kicks in.
    • If the generator goes out, you are down to sails. I would never want to be in a situation where I am on a lee shore or need power to get out of trouble and find that I have no engine propulsion to get me out of a bad situation.I have seen several electric boats stuck with a failed generator and unable to move until repaired. Why would a cruiser want to give up all these options and redundancy away?

While I run my engines as little as possible, they give me redundancy. Diesel engines remain the most reliable form of propulsion. It will take time, before an electric solution becomes more reliable.

Loss of Redundancy Reduces Charging Options

The diesel engines not only provide propulsion. With a large alternator, you have two good sources of battery-charging capability. And they heat water, while not vital for survival, cruising while taking cold showers in cold weather is not my idea of paradise.

Let’s look at charging sources on a conventional catamaran with an energy management plan that provides five independent battery-charging sources:

  • Two engines with large alternators and smart regulator on each one count as two sources as they are independent.
  • Solar
  • Hydro-generation
  • Generator.

On an electric catamaran, you could have combinations of solar, water regeneration through the main drives, and a generator. 

If the generator goes down at night when there is no solar generation and no wind to propel the boat to regenerate power to charge the batteries, you are basically dead in the water. 

Batteries will only last a short while especially since the entire boat relies on the battery bank to function

Forget the All-Electric Catamaran ...For Now

In my humble opinion, one can be extremely green with a conventional catamaran. The level of carbon elimination or “green-ness” depends on the individual crew and how they operate their boat. The more environmentally aware will tend to make choices that move them toward a lower carbon footprint.

With current technology (batteries, systems, and hardware), I do not believe a zero-emission boat is possible. That is, unless you have at least a crew of seven and six long oars and a drum.

My assessment of the lack of viability for carbon-free cruising was recently vindicated as I read Jimmy Cornell’s account of the challenges he faced while attempting to circumvent the globe carbon free in (article no longer available to link to). In his own words: “The only conclusion I could draw was that in its present form, the regeneration system, and implicitly the entire concept, was not working”.

He had a lot of courage to initiate the Elcano circumnavigation project with his zero-emission electric Outremer catamaran. Side note: Learn more about the Magellan-Elcano circumnavigation expedition from 500 years ago that Jimmy’s project commemorated.  He set out to do this already being fully aware of the reality of actually “walking the walk” and how much sailors rely on systems and propulsion. His account of the reasons why he had to abandon the project support my concerns.

Jimmy’s experience and information will go a long way to helping with the improvement and further development of this electric sailing technology which I am sure will one day be widely used. This is Oceanvolt’s rebuttal (supplier of the electric system on Jimmy’s cat) to Jimmy’s “shock” article about his experience with the all electric catamaran. 

When a reliable solution for zero-emission propulsion with good redundancy arrives as it surely will, we will be first in line to convert. In the meantime, we continue to operate our boat in a manner that leaves the smallest ecological impact possible to help protect our environment and way of life.”

On a side note: The famous YouTube couple, Sailing La Vagabonde, is also teaming up with Oceanvolt, who will supply the electric propulsion for their new emissions-free boat project! Yes, they are selling their Outremer and will go all-electric on their next boat. We are really excited to follow their progress and we will hopefully soon follow in their famous footsteps! Click to check out the announcement.

This from one of our followers: “I enjoyed your description of how you utilized your boat during the Arc Rally and I wonder what would have changed if you had electric engines? You would still have had to run the generator to supplement your renewable energy sources but then when you used the electric engines you would not have had the benefit of your alternators. I wonder if you might have ended up using even more diesel?

Interesting take from S/V Fagari: How do two 30-something-year-olds convert a 43-year-old sailboat to electrical propulsion and beat nearly 5,000 nautical miles eastward in the Caribbean? With a lot of luck, some hard work, and a fair bit of painful learning along the way – 5,000 Miles Against the Trades with an Electric Motor

What do you think? Please comment below. We would love to hear your input on the subject!

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