Vessel Profile: Hungry Like the eWolf

The eWolf all-electric tug in the San Diego Harbor. Photo: Crowley Maritime.

Crowley Maritime’s first all-electric tugboat begins its working life in San Diego.

Maritime industry firsts are always exciting, and the first American all-electric ship assist tugboat, the eWolf,  is no exception.

The 82-foot tug is now homeported in the Port of San Diego where it’s expected to be put to work this spring. Vessel owner Crowley Maritime accepted delivery of the vessel in January.

“The eWolf will provide services through its advanced vessel control technology and first-in-class energy features while providing the safety, quality and reliability that Crowley and our mariners are known for,” Crowley Shipping Senior Vice President and General Manager James Fowler said in a news release.

“Electric vessels have already been used in several marine applications for decades and the technology is now proliferating into the commercial space to a greater degree,” said Michael LaFleur, vice president of maritime at the Port of San Diego. “We have no doubt that we will see greater innovation in this space.”

Notably, the first Chinese-built, all-electric tugboat, the Yungang Electric Tug No 1, was delivered to its owners for Port of Lianyungang operations in 2021.

eWolf was constructed by Coden, Ala.-based Master Boat Builders and designed by Crowley’s Seattle-based Crowley Engineering Services.

“The eWolf demonstrates where the maritime industry can go, in terms of both innovation and sustainability, with solid partnerships between owners, designers, suppliers and shipyards,” Master Boat Builders President Garrett Rice said in a news release. “We are proud to have partnered with Crowley in the construction of the eWolf and look forward to seeing her at work in San Diego very soon.”

A rendering of the eWolf. Image: Crowley Maritime.

Although the integrated electrical propulsion system is supplied by ABB Marine, eWolf features some hardware from Schottel, based in Germany. The system includes two SRP 430 LE 2,050kW rudder propellers and a MariHub data IoT Gateway and monitoring solution.

On paper, the reported bollard pull of eWolf is around 70 short tons with a top speed of 12 knots powered by a Corvus Energy 6.2-megawatt-hour main propulsion battery. Additionally, the lack of a traditional stack pipe exhaust system frees up space above deck, providing a 360-degree view from the pilothouse.

Seattle-based Markey Machinery supplied eWolf’s DEPC-48 hawser winches. The DEPC-48 is fitted with several options for controlling the winches independently underway or joining both for in-port mooring.

These winches feature render and recovery functions with a drum brake that can hold-fast lines under about 306 tons of tension. The fabricated steel winch drum spans almost 31 inches with a 20-inch diameter core and flanges that measure about 58 inches in diameter.

The machines spool about 500 feet of 9-inch circumference high-strength, synthetic line rated to about 430 tons of breaking strength. An AC-variable frequency drive powers the winches that are geared to produce 289 feet-per-minute line speeds.

Crowley has also designed a microgrid shoreside charging station for the Port of San Diego to keep eWolf’s batteries topped off. “Regarding Crowley’s eWolf and shoreside microgrid project, the port made a commitment to assist in the permitting and planning of operations to satisfy environmental strategy goals within its Maritime Clean Air Strategy and to exceed state regulatory requirements for harbor craft,” LaFleur said. 

A public sector array of sticks and carrots contextualize how the eWolf came to be.

The vessel and charging station project is made possible by four grants that combined total about $13.67 million. Two worth $10.9 million came from the San Diego Air Pollution Control District, with one grant of over $2 million added by the U.S. Environmental Protection Agency (EPA) along with $750,000 from the federal Maritime Administration.

A 2020 executive order from California Gov. Gavin Newsom directing the state to transition all off-road vehicles and equipment to 100% net-zero emissions by 2035 also guides the region’s industry.

The state is also subject to California Air Resources Board regulations that are widely considered the strictest maritime emissions standards in the country. 

“The challenge of shoreside infrastructure to support electric vessels should not be underestimated,” LeFleur said. “Grid planning is complex and requires utility coordination, and new technologies such as batteries require policy adaptations that take time to implement.”

“As codes are adapted, this will become easier,” he continued. “However, for now, each project is a learning opportunity that is carrying us into the future.”

Crowley has stated that eWolf will generate 3,100 metric tons less carbon dioxide, 178 tons less nitrogen oxide and 2.5 tons less diesel particulate matter over the first 10 years of operations. According to EPA estimates, this is equal to sparing 350,000 gallons of gas from combustion.

ABB states that eWolf’s reduced emissions are roughly equivalent to 100 cars annually.

While carbon emissions tend to get much of the press, nitrogen oxide and diesel particulate matter are also environmental pollutants that can directly impact the health of those who breathe them in. Noise reduction also can be seen as pollution minimization and a crew health consideration. 

These reduced emissions are welcome, but as always one should consider the whole picture, including factors such as pollution costs of the energy source from which the vessel will draw.

San Diego Gas & Electric reports that 55% of the electricity the company delivers to homes and businesses comes from solar, wind and other renewable energy. San Diego also instituted a Climate Action Plan in 2022 to pursue zero-emissions targets for the city’s energy grid.

Another wrinkle in the eWolf story: ABB has stated that their installed technology systems will “enable maneuvering support and future remote operations,” so there is a possible future where the eWolf operates without crew aboard.

Are near-silent fleets of crew-less assist tugboats plying San Diego’s waters a utopian vision, a delusional investor fever dream, or an unsettling reality? Perhaps all three. One way or another, we’re all going to find out.   

Norris Comer is a Seattle-based writer and author. His debut memoir, Salmon in the Seine: Alaskan Memories of Life, Death, & Everything In-Between is now available wherever books are sold. You can find him on Substack, Instagram and at He can be reached via email at