Fuel & cost model
Once VPM knows where a vessel is going, it estimates what the voyage costs in fuel. This is the model that turns a vessel's machinery and speed into tonnes, a grade, a price and a CO₂ figure — and how far it can be trusted.
What it estimates
- Burn rate — tonnes per day, at the vessel's current speed and at its service speed.
- Grade — MGO, VLSFO, heavy fuel or LNG, with the right split inside and outside emission-control zones.
- Quantity, cost and CO₂ for the leg to the predicted next port.
- Autonomy — days of steaming left in the tank — and a bunker-need warning.
How it is built
The estimate is driven by two things about each vessel: how much power its main engine installs, and how fast it is moving through the water. Engine type is taken into account — a modern slow-speed engine is treated as more efficient than a medium-speed one, because it is. Auxiliary machinery and in-port load are added on top as a share of the main-engine figure.
Every input that matters here — installed power, service speed, engine model, fuel grade, tank capacity — comes from the vessel's technical profile, collected by hand. See Data & sources.
Calibrated to real consumption
A model built only from engineering rules of thumb drifts. VPM's is pinned to reality at one point: a real, reported consumption figure from one vessel's technical file — a known daily burn, at a known speed, laden. Every other vessel's burn rate is scaled from its own machinery and speed to match that anchor, which replaced an earlier assumed value that ran too high.
The model currently rests on a single measured datapoint. It has been checked against a handful of other vessels whose figures are known and lands close to each. When a second reported consumption figure surfaces, the calibration is re-checked against it. This is stated plainly because it is the model's main limitation.
Speed is almost everything
Fuel burn rises very steeply with speed — far faster than in proportion. As a rough guide, easing off about a fifth on speed can cut the burn rate by around half. This is why slow steaming works, and why VPM uses a vessel's actual AIS speed for its current burn rate rather than a nameplate figure. It also means the arrival-time estimate and the fuel estimate move together: a vessel that slows down to save fuel arrives later, and VPM reflects both.
Grade and emission-control zones
The Baltic and North Sea are sulphur emission-control areas, with a 0.1% sulphur cap. The real question for each vessel is whether it has a scrubber fitted and burns heavy fuel, or burns compliant fuel instead. VPM assigns each vessel a main grade and applies the zone rules per leg:
- A vessel with a scrubber keeps burning heavy fuel both inside and outside the zone.
- A vessel without one runs on a compliant low-sulphur grade — VLSFO or MGO — and, where its normal grade is not compliant inside the zone, switches down for that stretch.
- An LNG-fuelled vessel runs on gas throughout, with a small MGO pilot.
- Auxiliary engines are assumed to run on MGO.
Dual-fuel and LNG
An LNG dual-fuel engine runs most of its energy on gas with a small liquid pilot. VPM converts the energy demand into an LNG mass using the difference in energy content between the fuels, rather than swapping tonne for tonne. For a large LNG ro-ro this comes out at roughly 51 tonnes of LNG plus 3 tonnes of MGO per day — noticeably less than a like-for-like substitution from an oil-fuelled sister would suggest.
Distance: the real sea route
Leg distance follows the route a ship actually sails. VPM runs a route search over shipping-lane density grids — HELCOM for the Baltic, EMODnet beyond — that prefers known lanes but allows shortcuts through open water, and it takes the Kiel Canal when that is genuinely shorter than routing around Denmark. This replaced a flat percentage add-on to a straight-line distance, which over-stated many Baltic–North-Sea legs.
Cost to the next port
From the predicted next port, VPM measures the real sea-route distance, works out the steaming time at the vessel's speed, and applies the daily burn rate to get the fuel, cost and CO₂ for the leg. The figure is always shown next to the prediction's probability — "~9 t to Roomassaare, 28%" — so a low-confidence destination is never mistaken for a firm cost.
Tank, autonomy and the bunker warning
Tank capacity is taken per fuel where it is known; failing that, from a single tank figure plus a modest MGO reserve; failing that, estimated from the vessel's tonnage and flagged as an estimate. Autonomy is what remains in the primary-fuel tank set against the daily burn.
The bunker warning tracks how much of the quantity a user entered at the last stem has since been consumed. Once most of it is gone the row flags approaching; past the entered quantity it flags critical.
If a vessel stems a partial load into a large tank, "tank 40% full" tells you nothing useful. What matters is how much of the stemmed quantity is left. Before any stem is entered, VPM shows only burn rate and autonomy — it does not invent a tank level.
How good is it
It is an estimate, and it is presented as one. Calibrated to a single measured datapoint, checked against vessels whose figures are known, it produces daily burns ranging from a few tonnes for a small general-cargo ship to the order of eighty for a large ro-ro — each landing close to its known value. It is accurate enough to answer "roughly how much, roughly what it costs, roughly when they'll need more", which is the question a supplier is actually asking. It is not a substitute for a noon report.