The Electric Enigma

The Electric Enigma

Examining the pros and cons of clean propulsion

More electric boats are launching as battery technology and designs improve. Competition between builders worldwide is pushing innovation because larger electric boats can go faster, farther, and are quieter than ever. 

However, as the actual product is introduced, those boats must live up to, or exceed, the marketing hype. With today’s instant feedback platforms, e.g., social media, boats that fall short of expected performance face almost immediate criticism.

The pros and cons of electric boat ownership are similar to those of electric cars. Limited range, high cost, and low power might stop potential buyers. But zero emissions, no noise, and fewer moving parts can be enough to excite early adopters who also get drawn in by the “cool factor” of having the latest technology. 

Today’s electric boats bear little resemblance to the typical harbor cruisers like those from Duffy Boats, which are perfect for tootling around at slow speeds on calm water. Arc One, an electric boat built by SpaceX engineers, is a high-tech runabout that reaches 40 mph. Silent-Yachts’ 60-foot cruiser catamaran powered by solar panels is able to cruise at 10 knots.

Silent Yachts Solar Panel Battery Packs

In addition, electric outboards from companies such as Torqeedo and Vision Marine Technologies make motors for small runabouts and pontoons. Torqeedo offers electric outboards up to 80 horsepower and electric inboards up to 133 horsepower. Vision Marine Technologies’ E-Motion 180E outboard puts out the equivalent of 180 horsepower, enough to easily pull a skier or wakeboarder. 

The current challenges center around cost, technology, and the will of big manufacturers to make a significant investment in building all-electric boats. While gas-electric hybrid technology worked well in the auto industry as a bridge to today’s all-electric vehicles, hybrid tech simply doesn’t work well with boats in the less than 100-foot category, although that’s changing.

Cost is a Big Factor

“Currently, electric boats can be three times or more the cost of their internal combustion counterparts,” says Joseph Messler, a naval architect at DLBA Naval Architects in Chesapeake, Virginia. “We would expect costs to become more equivalent over time as battery prices come down. These are the most expensive components of an electrically powered boat.”

It is cheaper to run an electric boat because electricity is less expensive than diesel or gas. But unless you run the boat for thousands of hours a year for many years, it will be hard to make up for that initial cost. Even though fuel costs will disappear running on electric, a buyer shouldn’t do it simply to save money.

“You have to sell the electric boat concept on something like it’s good for the environment,” says Christopher Swanhart, director of recreational boats for DLBA Naval Architects. “It’s more efficient to charge a battery than it is to have your own power plant burning fuel on a boat. It’s also important to note that an electric boat is on the cutting-edge of technology. There’s a cool factor to that, like owning the latest iPhone.”

Technology—Good and Bad

“A big technology advantage for many electric boat owners is that it’s clean and quiet around the docks,” says Swanhart. “There is no noise or fumes when you are moving around at low speeds. At higher speeds, the water noise is the same no matter what the power is.”

For a naval architect, designing an electric boat presents major space and weight challenges. Because electricity doesn’t weigh anything, the boat won’t lose weight when the electricity is drained from the batteries, unlike a diesel-powered boat that gets lighter as fuel is burned. The naval architect can add batteries to provide the range the owner wants, but they take up space that cuts into the cabin area or room for other equipment such as a Seakeeper stabilizer or watermaker. 

There is also a point of diminishing return for every boat, where the added range or endurance of more batteries cannot surmount the increase in boat resistance.

“People also don’t use boats like they drive their cars,” says Messler. “You are supposed to charge your car battery regularly whether you drive that day or not. A boat can sit idle for a relatively long time. You could be gone on vacation for a month or two. If you have your own dock or are in a marina, it’s possible to keep it charged, but there could be complications like the parasitic loss of electricity due to a GPS or other equipment that is constantly running. You show up at the boat and realize you have only five percent juice and can’t move the boat.”

Limited cruising range is an important factor, too. Asking the question, “How long can an electric boat run at a constant speed of thirty-five knots?” focuses on what most consumers really want to know: The resistance of water on a boat hull is much greater than the resistance a car’s wheels encounter on the highway. Once you get
a car up to 40 mph, it takes about 15 horsepower to keep it going at that speed. Once a boat gets up to 40 mph, keeping it at that speed takes 150 to 200 horsepower for a similarly sized boat.

“Your readers can easily understand resistance of water in this example,” Messler says. “If you are going fifty mph on the highway in your car and you let off the gas, you will roll a considerable distance, but if you let off the throttle in a boat at forty knots, you are going to stop pretty quickly.”

Hybrid Limitations

Hybrid technology doesn’t work so well in boats less than 100 feet. “When you start hitting one hundred and twenty or one hundred and fifty feet with yachts and commercial boats, you see hybrid propulsion,” says Messler. “They can increase their endurance and range. In yachts, cruise ships, car ferries, commercial boats, and the U.S. Navy, it makes sense because you have the space to add the extra power system. It’s a hard sell to a client when you have to take away cabin space for a hybrid solution. Not everything scales down the way you want it to. But there are hybrid benefits, like increased range and quieter operation.”

Having two distinct types of propulsion systems also makes for maintenance challenges. The service requirements of both a diesel and an electric propulsion system make it more of a hassle, perhaps not worth it for some owners. Others, however, will accept the extra maintenance for the benefits. 

Manufacturer Motivation?

Major manufacturers, such as Brunswick, aren’t making huge investments in electric propulsion—yet. Business is increasingly robust with gas- and diesel-powered boats; it’s all builders can do to keep up with orders.

“I get the sense that big companies are monitoring what is going on with electric boats,” says Swanhart. “But right now, we don’t think they validate the reason to spend a lot of money to build an electric fleet of boats that people are not interested in buying yet. The consumer is holding off for all the reasons we have mentioned—price and lack of range.”

The winners in the competition to build better electric boats are the environment, the builders, and the end-users. In other words, everyone on the planet, and hopefully, we’ll all be able to enjoy the water without ever making a mark on it or in it. 

-by Doug Thompson

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