Ships do not run on tons of fuel. They run on energy. Image Credit: Fuelsure

Take a simple bunker purchase.

One supplier offers fuel at $600 per ton. Another offers $601.

Most buyers will go with the first one without thinking twice. Bunkers have long been bought this way: compare the price per ton and pick the lowest number.

But that comparison can be misleading.

If the second fuel delivers slightly more usable energy, the vessel may end up burning less of it to maintain speed. In that situation, the “more expensive” fuel can actually be the cheaper one once the voyage is complete.

This is a contradiction that has existed in the bunker market for years. Marine fuel is bought and sold by weight, yet ships do not run on tons of fuel. They run on the energy released when that fuel is burned.

That energy content, known as calorific value, determines how much propulsion a vessel receives from each ton loaded onboard.

As Kenneth Juhls, CEO of Tideform and AuctionConnect, notes:

“For decades bunker procurement has focused primarily on price per ton, yet the true economics of bunkering are far more complex. When energy delivered, operational disruption, and dispute outcomes are considered alongside price, it becomes clear that stronger transparency and better market intelligence are essential for helping procurement teams understand the real cost of fuel and make more informed decisions.”

This gap between price and performance is where calorific value becomes important.

Two fuels can meet the same specification and still perform differently. On paper they may look identical. In practice, one may deliver more usable energy to the engine than the other.

What makes this difference possible is something bunker buyers rarely discuss outside technical circles: calorific value.

Calorific value describes how much energy is contained in the fuel. It is typically measured in megajoules per kilogram. The higher the number, the more energy the engine receives when the fuel is burned.

In theory, this should be central to how marine fuel is evaluated. In practice, it rarely enters commercial discussions.

Historically that made sense. Fuel blends were more consistent, margins were wider, and small differences in energy content were often absorbed within normal operational variation. Buyers focused on the number that was easiest to compare, the price per ton.

Fuel blending today is far more complex than it was a decade ago.

Very low sulphur fuel oils in particular can be produced from a wide range of refinery streams. Two compliant fuels can meet the same specification and still differ meaningfully in energy content. Those differences are not visible in the invoice price.

The result is that two fuels which appear equivalent in the market can perform quite differently once they are burned onboard.

For operators running a single voyage the impact may be subtle. Across an entire fleet and hundreds of stems it becomes far more noticeable.

Energy delivered is only part of the picture.

The true cost of bunkering also appears in operational factors that rarely show up in the initial price discussion. Quantity differences between barge delivery figures and onboard measurement can affect how much fuel a vessel actually receives. Delays during bunkering can disrupt schedules. Quality disputes can lead to claims, additional testing, or operational adjustments.

Individually these issues may seem small. Taken together across multiple deliveries they can materially affect operating cost.

For many years these effects were difficult to quantify. Much of the relevant information sat in separate operational systems such as bunker delivery notes, laboratory results, Statements of Facts and claims records, without an easy way to analyse them together.

That is beginning to change.

As more operational data becomes available, buyers are starting to evaluate suppliers based on how fuel performs in practice rather than relying solely on price comparisons. Historical delivery outcomes, claims records and energy performance can now be assessed alongside commercial pricing.

Platforms such as Fuelsure are starting to bring these datasets together, allowing procurement teams to look beyond invoice price and examine how fuel actually behaves across real deliveries.

The result is a clearer picture of bunker economics.

In some cases the cheapest fuel remains the best choice. In others, small differences in energy delivered or operational reliability outweigh a minor price advantage. What matters is that buyers can now begin to see the difference.

None of this means the bunker market will stop quoting prices per ton. Price benchmarks will remain an important reference point in negotiations.

But as operators gain better visibility into fuel performance, the industry is likely to become more aware of the gap between price and true cost.

The distinction is simple.

Ships do not run on tons of fuel.

They run on energy.

And the bunker buyers who understand that difference will be better positioned to manage fuel costs in an increasingly complex market.