Beginning this fall, commuters in Stockholm will have a new public transportation option when traveling between City Hall and the suburb of Ekerö: an electric hydrofoil ferry that flies above the water—and uses up to 80% less energy than traditional diesel ferries.
The ferry is from Candela, a Swedish company that first launched a prototype of an electric hydrofoil vessel in 2016. Because of the limits of battery technology, boats have been difficult to electrify. Lithium-ion batteries are less energy dense than diesel or gasoline, so replacing all the fuel a vessel needs would require batteries too big and heavy for it to carry. That’s where hydrofoil technology comes in: like wings underneath a boat, hydrofoils lift a vessel out of the water so that it essentially flies along its surface, reducing both drag and the amount of energy it needs.
With hydrofoils, Candela’s boats are allowed to travel faster than traditional speed limits. In Stockholm, for example, ferries are limited to a 12-knot speed (about 13 miles per hour) so that they leave no wake. Those waves made by a boat can affect other vessels and damage shore lines or dock infrastructure. But Candela’s electric hydrofoil ferry, called the P-12, is exempt from that limit; by hovering above the surface of the water, it doesn’t create a wake. At about 20 knots (23 miles per hour) it starts to lift off, and it can reach a cruising speed of 30 knots, or about 35 miles per hour.
With that speed, the Candela ferry is expected to drastically cut commuter times for Stockholm residents. Travel between Stockholm’s city hall and Ekerö is about 18 kilometers, or 11 miles. There’s currently a ferry that makes that route, but it takes an hour; Candela’s P-12 will cut that in half. Taking the ferry also avoids the traffic that can make a car trip take more than 45 minutes. This new pilot project will be the first time that Candela has launched a ship for public transit.
Candela’s P-12 commuter ship fits 30 passengers (the company also makes two models for private use). That’s quite a bit smaller than other ferries: Stockholm’s diesel commuter ferries (including the one that currently travels to Ekerö) can fit about 340 people—but Candela says their average occupancy rate is only around 10%. “By switching from almost empty big vessels to a system where you have larger fleets of smaller, nimbler vessels, you can get more frequent departures and shorter travel times,” says Mikael Mahlberg, Candela’s head of communications. “You end up with a more bus-like system but on water, which has a lot of benefits for passengers and the environment.”
Candela sees its ferry as a way to revolutionize city transportation. Many cities around the world are built on the water, and that water was once the main way to get around. But then came cars—and all their traffic. Some cities have implemented policies like congestion pricing (Stockholm among them) to reduce traffic and vehicle emissions. But to Candela, waterways are being underused, and current vessel options are generally polluting.
Without emissions controls, diesel ferries can release more nitrous oxide and particulate matter pollution per passenger trip than if those riders commuted by car. Because they’re electric, Candela’s boats don’t release any exhaust emissions. A 2022 lifecycle analysis on Candela’s P-12, performed by students at the KTH Royal Institute of Technology in Stockholm, found that the electric hydrofoil ferries emit 97.5% less carbon dioxide emissions than diesel ferries.
Recently, Candela offered test rides in New York Harbor as a way to demonstrate its technology and meet potential customers. If New York used Candela’s electric hydrofoil ferries, a trip between Manhattan’s Chelsea Market and Hoboken Terminal could take less than three minutes, the company says. (That trip can only currently be done by car or train, and takes about half an hour either way). A ride from Staten Island’s ferry terminal to lower Manhattan currently takes about 25 minutes; Candela says it could do it in 11.
The company hints at several clients in the U.S. being close to signing contracts for its ferries, and it recently announced that Neom, a “megacity project” in Saudi Arabia, procured eight of its P-12 ships. They’ll be delivered in 2025 and early 2026.