H Nordic maritime fuel savings are calculated from three standard inputs: annual operating hours, diesel consumption rate per kWh of electricity generated, and bunker fuel cost per tonne. A shadow reduction factor is applied to multi-turbine configurations. Aerodynamic drag reduction is excluded from the table entirely -- it is a real additional saving but is not included in the published figures.
Annual operating hours: 6,500 hours per year.
This is a standard commercial vessel operating profile used as the baseline across all configurations. Vessels with higher utilisation -- bulk carriers and tankers on continuous trading routes, for example -- will generate proportionally more. The calculation scales linearly with operating hours: a vessel running 7,500 hours per year generates approximately 15% more than the table figures.
6,500 hours represents approximately 74% annual utilisation, accounting for port calls, scheduled maintenance, and seasonal variations. For many commercial routes this is a conservative figure.
Diesel consumption rate: 0.295 kg per kWh.
This is the standard conversion factor for marine diesel generators operating at typical load. It represents the fuel burned by the generator to produce one kWh of electricity -- the fuel that turbine-generated electricity displaces.
The figure is well established in marine engineering and is consistent with published data from major generator manufacturers. It applies to medium-speed marine diesel generator sets operating at 60 to 80% load, which is the typical operating condition for shipboard electrical generation.
Fuel cost: USD 700 to 1,000 per tonne.
The range reflects prevailing bunker fuel price volatility. The table shows savings at both ends of the range. Operators with fuel hedging arrangements should use their effective all-in cost. At prices above USD 1,000 per tonne -- within the historical range -- savings and payback periods improve proportionally.
In a multi-turbine installation, turbines positioned downwind of other units operate in their partial wake -- a zone of reduced wind speed and increased turbulence behind the upstream turbine. This reduces output at the affected positions.
A 10 to 30% shadow reduction is applied across all multi-turbine configurations in the published figures. The precise reduction depends on deck layout and the separation between units. The range used in the table is deliberately conservative -- actual shadow losses in an optimised deck layout are typically at the lower end of this range.
The deck layout assessment that is part of every H Nordic installation optimises turbine positions to minimise shadow interactions, so real-world performance typically exceeds the conservative published figures.
Applying these inputs:
For a four-turbine 100 kW configuration producing an average output of ~120 kW across 6,500 operating hours, annual electricity production is approximately 780,000 kWh. At 0.295 kg/kWh, that displaces approximately 230 tonnes of diesel per year. At USD 700 to 1,000 per tonne, the annual saving is USD 161,000 to 230,000.
Aerodynamic drag reduction.
The published fuel savings figures cover direct electricity generation only. They do not include the additional saving from aerodynamic drag reduction through vortex disruption at the superstructure edges.
As documented by the Stena Jutlandica experience -- where 4 kW of installed turbines produced 80 to 90 tonnes of annual fuel saving -- drag reduction can exceed direct generation saving significantly. H Nordic excludes it from the published table because it requires a vessel-specific aerodynamic assessment to quantify reliably. It is a real and material saving for most vessel geometries, particularly car carriers and RoRo vessels.
Fuel price increases.
The calculation uses the current USD 700 to 1,000 per tonne range. Historical bunker fuel prices have shown a long-term upward trend with significant volatility. The payback period improves -- and lifetime savings increase -- at higher fuel prices.
EU and Nordic funding support.
Grant support under EU or Nordic maritime decarbonisation programmes directly reduces net capital outlay and shortens payback. This is not included in the base calculation.
See also: Full fuel savings model · The Stena Jutlandica explained
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