Our Electrifying World is a series about how electrification is creating a more sustainable energy transition. It is sponsored by Rewiring America.
On a brisk February morning in Miami, Matthew Creswell watched as engineers wrestled thick power cables at a cruise ship terminal. The ship was about to plug into the electrical grid — an event far less ordinary than it sounds.
As the harbormaster of Juneau, Alaska, Creswell was there to study the Port of Miami’s $125 million shore power project through an American Association of Port Authorities program. He hoped that what he learned would shape Juneau’s own electrification plans.
“In our homes and our daily lives, we plug things in and power works,” he says. “Plugging a cruise ship in is like essentially adding a small town to your electrical grid for a few hours in the day.”
Smaller vessels frequently plug into shore power, getting electricity while at berth with shut-down engines, which may make this seem like an underwhelming technical achievement. However, when it comes to scaling up shore power for cruise ships weighing hundreds of thousands of tons, logistics, engineering and grid infrastructure present significant hurdles many ports struggle to surmount.
As a result, a lot of cruise ships run their engines full time to power onboard generators for their electrical needs — burning endless gallons of fuel in the process.
Right now, only a small number of ports visited by cruise ships — fewer than three percent — have shore power. But that’s beginning to change. This year, Seattle became the first U.S. port to offer shore power at all three of its cruise ship berths. Other ports, including Miami, Juneau and Vancouver, are following suit. The Cruise Lines International Association reports 33 ports worldwide now have shore power, with 24 funded projects and 18 more planned.
The Port of Seattle’s shore power evolution began with a simple idea: use the city’s hydropower to eliminate docked ships’ diesel emissions. But implementing it proved anything but simple.
One of Seattle’s terminals has operated shore power for cruise ships since 2004, initially funded by the cruise line Holland America Group. To bring shore power to a new pier and avoid disruptions for downtown, the port installed a mile-long submarine cable while negotiating with local tribes to protect fishing rights.
In the early 2000s, the port’s team discovered it needed multiple connection points at each terminal for different ships’ power inlet locations. “When you go to gas up your car, you just have to be on the right side of your gas tank. Shore power installation is not standard,” explains Linda Springmann, who leads the cruise program. “Sometimes it’s port side, sometimes it’s starboard on a ship. And what we’ve also found is there are some brands who, rather than having the shore power at the aft [stern] end of the ship, they have installed it [amidships, meaning in the middle]. You have to have as much flexibility as you can.”
The results — which took two decades and over $50 million in infrastructure investments — reduce diesel particulate emissions by 80 percent and CO2 emissions by 66 percent compared to ships running their engines.
Last year, about 43 percent of cruises plugged into shore power. The hope is that the third shore-powered berth will immediately bring that number up to 60 or 70 percent, reaching 100 percent by 2027, Springmann says.
Still, shore power covers only part of the journey: “We know it’s not solving the whole cruise itinerary,” Springmann says. “But to have them shut off their engines within an hour of arrival and then restart the engines before they depart has been a really big benefit.”
Not everyone agrees. Seattle Cruise Control founding member Elizabeth Burton views the port’s portrayal of shore power as a major accomplishment as greenwashing because of its minor impact. Burton points to the port’s 2024 cruise dashboard: “The entire season’s shore power eliminated almost 4,000 tons of CO2,” she says. “But for their entire journey to Alaska and back for every ship, the ship will emit 1.5 million tons.” Less than one percent. She sees the port’s goals to keep growing in cargo, cruise traffic and international flights as at odds with environmental goals. She concedes that shore power reduces health harms to people living and working near the terminals, but “it’s not going to solve our climate problem,” she says.
While Seattle built its system incrementally, Juneau faces pressure to implement shore power faster. The Alaskan port actually pioneered the technology in 2001 at its privately owned South Franklin Street Dock, proving the concept could work. Now, with 1.7 million cruise passengers expected this season — over 50 times Juneau’s permanent population — the push to expand shore power has intensified.
But Juneau’s circumstances make Miami’s or Seattle’s solutions difficult to replicate. The port’s floating docks, rebuilt in 2015 to handle larger ships, must accommodate extreme 25-foot tidal swings — the second-highest in North America. This rules out fixed cable systems. When Creswell consulted Miami’s engineers about using submarine cables, they warned of the risk of damage caused by whales. Instead, Juneau is designing floating power stations that can move with the tides.
Power availability is another hurdle. While Juneau runs on renewable hydropower, the local utility estimates it can support shore power for one in every four ships in an average year. “If it’s a low water year, there’ll be no power available at all because we’re 100 percent hydro up here,” he says.
The Port of Miami’s $125 million project offered Creswell both inspiration and cautionary tales. The Florida port installed shore power at five terminals but can only power three ships simultaneously due to Florida Power & Light’s grid constraints.
Though the environmental benefits are clear — the annual green house gas emission reduction is equivalent to removing 2,470 cars from the road, according to a 2023 analysis by Moffat and Nichol — the business case for shore power in Miami remains harder to make. The port charges cruise lines $4,115 per connection plus fees, but even at these rates, the return on investment is minimal.
Juneau faces its own funding dilemma. After spending $53 million to rebuild its docks in 2016 to 2017, the port needs another $60 to $80 million for electrification.
“We know how expensive it is,” Creswell says. “It’s the kind of project that will never pencil out financially, but then you have to weigh the environmental gains versus the cost.”
Even if Juneau adopts Miami’s fee structure, projected revenues of $1.3 million annually would barely cover estimated operating costs. A pending $65 million Environmental Protection Agency Clean Ports Grant could bridge the gap, but competition is fierce.
Some funding may come from passenger fees. The City and Borough of Juneau collects $13 per cruise passenger through various taxes and fees, generating about $22 million annually. But diverting these funds to shore power would delay other infrastructure projects.
Still, for Seattle, Miami and Juneau, shore power combines environmental responsibility with economic pragmatism.
Springmann and others are hoping many more ports can figure out ways to add shore power. Other ports should “talk to us, talk to Miami, talk to the port of Rotterdam and various entities who have already installed it.” says Springmann. “Maybe they can get some shortcuts.”