Shipping moves roughly 90% of global trade and generates close to 3% of worldwide emissions. Cleaning up the sector has proved difficult because oceangoing cargo ships can spend weeks between ports and typically burn heavy fuel oil—cheap, energy-dense and highly polluting.
Global efforts to reach net-zero shipping through cleaner fuels have faced political and commercial headwinds. But there may be another route: as battery prices decline year after year, electrification could play a larger role—without trying to replace liquid fuel entirely.
Electrification already works—on short routes
Electric ferries now carry passengers and cars on short crossings, and ports are beginning to adopt electric tugs and inland freight vessels. The reason is simple: these operations can recharge at berth and don’t need ocean-level endurance.
The big question is whether electrification can ever matter for container ships crossing oceans. Oil’s energy density lets these giants sail from Asia to Europe without refuelling, while batteries remain too heavy and expensive to substitute fuel on a one-for-one basis.
Not “all or nothing”: batteries alongside fuel
Electrification does not have to be binary. Batteries can be used in parallel with conventional fuels. Two main approaches are emerging:
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Onboard batteries charged in port
This is the intuitive model, similar to electric cars and trucks: install batteries on the ship and recharge in port (and, ideally, wherever charging becomes possible along the route). The challenge is the high upfront cost and the need for frequent, reliable charging opportunities.
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A global fleet of dedicated “battery support vessels”
Here, container ships would be built or retrofitted to run on fuel or electricity, then connect at sea to smaller battery vessels that sail alongside and supply stored electrical energy. The battery vessel later detaches and heads back to port to recharge—effectively turning energy into a maritime logistics service.
Battery vessels already exist in niche applications, suggesting that scaling the concept is technologically plausible—even if operationally complex.
What modelling suggests on an Asia–Europe route
In one model, a container ship sailing from China to Northern Europe could draw power from battery vessels on coastal segments where ports and charging are readily available (for example, between Chinese ports and Singapore). It would then switch to fuel across stretches with little nearby land-based infrastructure, before returning to battery support through regions where renewable energy is abundant and charging can be organised.
However, when the ship must rely on battery vessels for several consecutive days far from shore, the economics only work if marine-grade batteries become extremely cheap—on the order of less than A$100 per kWh. Under the modelled assumptions, completing the full China–Northern Europe run would require dozens of battery vessels to support a single container ship.
The economics: massive onboard batteries are hard to justify
The modelling indicates that very large onboard battery installations are not cost-effective today. Outfitting a New Panamax container ship with a battery in the hundreds of megawatt-hours would cost tens to hundreds of millions of dollars, and even a fully charged battery would only propel the ship for a limited period.
To pay back such an investment, the battery must be used frequently—yet ocean passages and rerouted voyages (for example, around the Cape of Good Hope rather than through the Red Sea) could leave expensive battery capacity idle for weeks.
That’s why the battery support vessel concept may be more promising: it enables a gradual, flexible rollout—starting where distances are shorter, renewable power is cheaper, and charging infrastructure can be built out.
What could accelerate adoption
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continued battery cost declines, especially for marine-certified systems;
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wider adoption of carbon pricing on shipping fuels, improving electricity’s competitiveness;
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ship designs and retrofits that enable meaningful electric propulsion (though converting large drivetrains may impose an efficiency penalty).
Fuel is one of the biggest cost items in shipping: large container vessels can burn over 100 tonnes per day. Even partial electrification on select route segments could therefore reduce emissions and potentially improve economics—especially when fuel prices or carbon costs rise.
Looking ahead
Gigantic battery packs on ocean-going container ships are unlikely to make financial sense in the near term. But hybrid electrification, particularly via battery support vessels, could become a practical bridge toward lower-emission shipping. Even if the concept ultimately proves difficult at scale, it is compelling enough to deserve serious testing and further analysis across technology, operations and policy.
