By Sune Strøm, Stillstrom’s Senior Regulatory and Public Affairs Manager

At Stillstrom, our mission is to eliminate vessel emissions through our integrated offshore power and charging solutions. A regulatory shift long in the making and implemented this month is now working in the same direction. The UK Emissions Trading Scheme (UK ETS) now extends to maritime, turning carbon into a direct operating cost for ship owners and offshore wind developers alike.

The service operation vessels (SOVs) servicing UK wind farms are therefore about to feel a new cost pressure that has nothing to do with turbine output or capacity factors. Carbon emissions from these vessels are no longer an environmental consideration alone, they are becoming an operating cost that developers and their supply chains need to plan for.

The UK ETS is not a new concept. Power generators and heavy industry have operated within it since 2021. The principle is straightforward - a cap is set on total emissions across covered sectors, operators must surrender one allowance for every tonne of CO₂e they emit, and the cap reduces over time. What is new is that vessels of 5,000 gross tonnage and above are now entering the scheme for domestic UK voyages, with greenhouse gas (GHG) emissions included alongside those generated during transit. Every tonne of MGO burned on a vessel at berth, idling at sea or during voyage will emit more than 3 tonnes of CO₂. The statutory civil penalty carbon price for 2026 is set at £49.41 per tonne.

While the market price for allowances will fluctuate, the direction of travel is clear, and emitting carbon carries an increasingly measurable financial consequence. For example, over the course of a year, a ship burning around 1,500 tonnes MGO emits around 4,800 tonnes of CO₂e. If the vessel owner ends up paying the current statutory rates, then the use of 1,500 tonnes of MGO will add a yearly additional cost of £240,000, before accounting for the fuel itself (and assuming the penalty price is in effect). Across a fleet, those costs quickly become material.

The case for switching to electric now

Offshore wind farm owners in UK waters who are using the larger SOVs for daily maintenance, will also come into scope for UK ETS costs from 1 January 2027 . The solution, however, is closer to hand than it might appear. By switching from fossil-fuelled ships to battery-electric vessels (E-SOVs), developers and their vessel providers can eliminate those GHG emissions at source, charging onboard batteries by tapping directly into the offshore wind farm’s own power production. . Stillstrom's integrated charging systems are built for exactly this, enabling hybrid and electric vessels to connect to clean electricity while offshore. Implementing a “Wind-to-Ship” model not only avoids GHG emissions and associated costs, it also cuts exposure to oil price volatility and the geopolitical pressures driving it up.

Why standing still is no longer an option for shipowners

UK ETS does not distinguish between a vessel making progress and one running generators alongside a quay or at anchor - a tonne is a tonne. That creates a direct financial incentive to reduce GHG emissions during idle and service periods, not simply just while their journey is underway.

The logic that makes E-SOV electrification compelling applies across maritime more broadly. . Every period a ship can connect to zero or near zero carbon electricity instead of running auxiliary diesel generators minimises both fuel consumption and the number of emissions allowances that must ultimately be surrendered. As carbon pricing becomes embedded across maritime, the value of that operational flexibility will only increase.

The UK ETS threshold currently sits at 5,000 GT. It would be a mistake to treat that line as a target to stay just beneath. The UK Government has already consulted on extending the scheme to international voyages from 2028, and a review of the gross tonnage threshold is scheduled for the same year. Vessels below 5,000 GT are not outside the direction of policy, they are simply only outside its current scope. That is a distinction, but probably not a permanent one.

More fundamentally, the North Sea is undergoing significant change. Offshore wind energy represents one of the largest concentrations of marine activity anywhere in the world over the coming decade. This will unlock power supplies at large scale not only onshore but also offshore and thereby enabling maritime electrification both in ports and at sea.

At sea the introduction of Offshore Power Zones connected e.g. to offshore wind farms will be able even in the shorter run to power idling vessels at sea where ships are anchoring. Today around 75 vessels are daily idling across UK waters. These emit yearly more than 230,000 tonnes of CO2e – an emission and cost that can be reduced by tapping into offshore power zones at sea. This is one of three priority pathways we see for offshore power supply and charging - the full electrification of battery-powered SOVs in offshore wind farms, charging directly from the development's own power production; and Offshore Power Zones delivering power both to idling vessels at sea outside ports and anchorage zones, and to short sea cargo vessels at likely charging capacities of 20MW and above.

As the power infrastructure for maritime use in ports and at sea expands, vessels capable of making use of it will be better positioned to capture both operational savings and commercial opportunities. Our recent whitepaper with Baltic Energy Island and Port of Rønne explores exactly this model. Bornholm Energy Island – Powering Maritime Electrification sets out how offshore wind energy can accelerate maritime electrification.

The operators best placed to compete may not simply be those with the newest fleets, but those with the greatest operational flexibility and accessto competitively priced electricity. In essence, the ability to connect to power in ports and at sea where available, reduce generator hours, switch between power sources and adapt as regulation evolves. Carbon pricing rewards decarbonised energy sources like renewable power and in combination with energy efficiency gains for battery-electric propulsion and being powered during idling the business case for going decarbonised via electrification is becoming more and more attractive.

UK ETS, EU ETS and FuelEU are providing clear price signals for the cost of emitting GHGs in ports and the seas around UK and EU. The postponed decision on the IMO's Net-Zero Framework is therefore not a crutch for ship owners, as UK and EU GHG-emission regulation are already in place today.

For years, carbon has largely been treated as an externality, sitting outside the core financial calculations of vessel operations. Increasingly, it will sit alongside fuel, labour and insurance as another input that owners must actively manage. For maritime and offshore wind energy businesses alike, standing still no longer simply costs just time and fuel. It carries a carbon price too. Go electric avoiding fluctuating fossil fuel prices and increasing GHG-emission costs. It already makes sense for road transport; it makes similar sense for shipping.