Educational scenario tool

Boil-Off Gas & Propulsion Economics Calculator

Explore how cargo volume, voyage profile, propulsion gas demand and reliquefaction interact over a voyage. Every parameter is an assumption you enter and can change.

Results are indicative and depend on the assumptions entered. They do not replace maker data, ship design documentation, operational procedures or engineering analysis.

Scenario inputs

Vessel and cargo

Vessel capacity [m³ LNG]

Cargo fill level [%]

LNG density [kg/m³]

Depends on cargo composition. Editable assumption.

BOG rate [% of cargo/day]

Entered manually. No rate is assumed from vessel type.

Cargo temperature (reference only) [°C]

Displayed for reference. It does not affect any result — no sourced BOG-versus-temperature correction model is configured.

Voyage

Voyage distance [NM]

Vessel speed [knots]

Sea margin [%]

Waiting / port time [hours]

Propulsion

Propulsion type alone does not imply a fuel consumption. Values below must be entered from maker, class or operator documentation.

Propulsion concept

Low-pressure two-stroke dual-fuel engine using the Otto cycle on gas, commonly combined with a low-pressure gas supply system.

Input mode

Daily LNG-equivalent gas demand for propulsion [t/day]

Gas demand compared against natural BOG — not total consumption of all fuels. Use verified vessel or operator data; any other value is your own illustrative assumption, not a typical figure.

If gas demand exceeds natural BOG

Reliquefaction

Reliquefaction plant in service

Recovery efficiency [%]

Maximum plant capacity [t BOG/day]

Specific energy consumption [kWh/t BOG processed]

Energy price [USD/kWh]

Economics

No prices are fetched from any market source. Every price below is an editable assumption you enter yourself. A price left at 0 is treated as not set and its monetary results are hidden.

Currency

LNG cargo value [USD/t LNG]

Auxiliary fuel price [USD/t fuel]

Carbon price [USD/t CO2e]

Results

Voyage and cargo

Voyage duration: 19.52days
Sea time: 17.52days
Waiting / port time: 2.00days
Initial LNG cargo: 170,520m³
Initial LNG cargo: 76,734.0t

Cargo balance on arrival

Initial cargo: 76,734.0t
Natural BOG generated: 1,498.2t
Forced boil-off: 0.0t
LNG recovered: 0.0t
Estimated final cargo on arrival: 75,235.8t
Estimated final cargo on arrival: 167,191m³
Cargo retained: 98.05%

Boil-off gas

BOG rate (as entered): 0.100% cargo/day
Daily BOG: 170.5m³/day
Daily BOG: 76.73t/day
Total BOG generated: 1,498.2t

Propulsion gas balance

Model strategy: Use natural BOG for propulsion first; reliquefy surplus.

LNG-equivalent gas demand: Requires administrator data
Natural BOG used as propulsion fuel: Requires administrator data
Forced boil-off from cargo: 0.0t
Additional auxiliary fuel for BOG deficit: Not used in this strategy
Uncovered gas deficit: 0.0t
Gas deficit energy: Not applicable
Pilot fuel: Requires administrator data
Total liquid fuel (profile + BOG deficit): Not applicable

gasDeficitEnergy [MWh] = gasDeficit [t] × LNG LHV [MWh/t]

auxFuel [t] = gasDeficitEnergy [MWh] ÷ auxiliary fuel LHV [MWh/t]

auxFuelCost = auxFuel [t] × auxiliary fuel price [per t]

LNG tonnes are never converted 1:1 into auxiliary fuel tonnes.

Surplus and reliquefaction

Surplus BOG after propulsion: Unavailable — propulsion demand is not configured
BOG processed by reliquefaction: Unavailable — propulsion demand is not configured
LNG recovered to cargo: Unavailable — propulsion demand is not configured
Reliquefaction losses: Unavailable — propulsion demand is not configured
Unprocessed surplus (reliquefaction capacity exceeded): Unavailable — propulsion demand is not configured
BOG sent to GCU / unhandled surplus: Unavailable — propulsion demand is not configured
Reliquefaction energy: 0kWh

Economics

Recovered LNG value: Not set
Reliquefaction energy cost: Not set
Net reliquefaction savings: Not set
Pilot fuel cost: Requires administrator data
Profile liquid fuel cost: Not applicable
Additional auxiliary fuel cost for BOG deficit: Not applicable
Total liquid-fuel / bunker cost: Not set
CO2e: Requires administrator data
Methane slip: Requires administrator data

Total liquid-fuel / bunker cost is the sum of pilot fuel, profile liquid fuel and fuel used to cover a BOG deficit. It does not include cargo value or reliquefaction energy cost.

Distribution

Where the boil-off gas goes

Total natural BOG

1,498.2 t

Disposition: Unavailable — propulsion demand is not configured. Unknown propulsion demand is not treated as zero demand, so no split between propulsion, reliquefaction and GCU is calculated. Enter a daily gas demand (from verified vessel or operator data, or as your own illustrative assumption) to see the allocation.

Allocation order: Use natural BOG for propulsion first; reliquefy surplus. Reliquefaction losses are included within GCU / unhandled and are not counted twice.

Voyage profile

Daily profile

Constant-rate illustrative estimate based on the initial cargo. This is not a step-wise cargo simulation.

BOG generated / day: 76.73 t
Gas demand / day: Requires administrator data
Reliquefied / day: Not active

BOG generated

Day 20 is a partial voyage day (≈0.52 day); its values are pro-rated.

Daily BOG profile values in tonnes
Day	BOG generated
1	76.73
2	76.73
3	76.73
4	76.73
5	76.73
6	76.73
7	76.73
8	76.73
9	76.73
10	76.73
11	76.73
12	76.73
13	76.73
14	76.73
15	76.73
16	76.73
17	76.73
18	76.73
19	76.73
20 (partial, 0.52 day)	40.25

Results are indicative and depend on the assumptions entered. They do not replace maker data, ship design documentation, operational procedures or engineering analysis.

Propulsion concept comparison

Same vessel, voyage and economics assumptions for every concept. Differences come only from the propulsion parameters you supply.

Propulsion concept comparison under identical assumptions
Concept	Gas demand	BOG to propulsion	Surplus / deficit	Net savings
Steam turbine	Requires administrator data — no sourced parameters configured for this concept.
DFDE / TFDE	Requires administrator data — no sourced parameters configured for this concept.
ME-GI	Requires administrator data — no sourced parameters configured for this concept.
X-DF	Requires administrator data — no sourced parameters configured for this concept.

Assumptions and parameter sources

Data set version 2026.09-0. Parameters marked as requiring administrator data have no verified public source configured, so the calculator never substitutes a value of its own. You may enter your own value in advanced mode; results are then based on your assumptions.

Allocation strategy: Use natural BOG for propulsion first; reliquefy surplus. If gas demand exceeds natural BOG, the deficit is handled by the strategy selected in the form.

Propulsion profile parameters, units, ranges and sources
Concept	Parameter	Value	Unit	Range	Source / note
Steam turbine	dailyGasDemand	Requires administrator data	t LNG-equivalent/day	0–500	Daily LNG-equivalent gas demand for propulsion. Requires vessel-specific shop-test or operator data.
Steam turbine	propulsionPower	Requires administrator data	MW	0–100	Installed propulsion power. Requires maker or classification documentation.
Steam turbine	loadFactor	Requires administrator data	%	0–100	Average load over the voyage. Requires operator voyage data.
Steam turbine	thermalEfficiency	Requires administrator data	%	1–100	Fuel-to-shaft efficiency of the propulsion chain. Requires maker data.
Steam turbine	gasShare	Requires administrator data	%	0–100	Share of fuel energy supplied as gas. Requires maker data.
Steam turbine	lngLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the LNG actually carried. Depends on cargo composition; requires a cargo document or verified reference value.
Steam turbine	pilotShare	Requires administrator data	%	0–20	Share of fuel energy supplied as pilot fuel. Requires maker data.
Steam turbine	pilotFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the pilot fuel. Requires a fuel analysis.
Steam turbine	auxFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the auxiliary liquid fuel. Requires a fuel analysis.
Steam turbine	co2eFactor	Requires administrator data	t CO2e/t fuel	0–10	Well-to-wake or tank-to-wake CO2e factor. Requires a defined regulatory or published source.
Steam turbine	methaneSlip	Requires administrator data	% of methane supplied to the engine	0–10	Unburned methane leaving the engine, as a scenario assumption for a specific engine and load — not a universal characteristic of a propulsion type. Requires maker measurement or a published study stating its basis.
Steam turbine	methaneFraction	Requires administrator data	% CH4 by mass in gas fuel	0–100	Methane mass fraction of the gas actually burned. Depends on cargo composition; requires a cargo document.
DFDE / TFDE	dailyGasDemand	Requires administrator data	t LNG-equivalent/day	0–500	Daily LNG-equivalent gas demand for propulsion. Requires vessel-specific shop-test or operator data.
DFDE / TFDE	propulsionPower	Requires administrator data	MW	0–100	Installed propulsion power. Requires maker or classification documentation.
DFDE / TFDE	loadFactor	Requires administrator data	%	0–100	Average load over the voyage. Requires operator voyage data.
DFDE / TFDE	thermalEfficiency	Requires administrator data	%	1–100	Fuel-to-shaft efficiency of the propulsion chain. Requires maker data.
DFDE / TFDE	gasShare	Requires administrator data	%	0–100	Share of fuel energy supplied as gas. Requires maker data.
DFDE / TFDE	lngLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the LNG actually carried. Depends on cargo composition; requires a cargo document or verified reference value.
DFDE / TFDE	pilotShare	Requires administrator data	%	0–20	Share of fuel energy supplied as pilot fuel. Requires maker data.
DFDE / TFDE	pilotFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the pilot fuel. Requires a fuel analysis.
DFDE / TFDE	auxFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the auxiliary liquid fuel. Requires a fuel analysis.
DFDE / TFDE	co2eFactor	Requires administrator data	t CO2e/t fuel	0–10	Well-to-wake or tank-to-wake CO2e factor. Requires a defined regulatory or published source.
DFDE / TFDE	methaneSlip	Requires administrator data	% of methane supplied to the engine	0–10	Unburned methane leaving the engine, as a scenario assumption for a specific engine and load — not a universal characteristic of a propulsion type. Requires maker measurement or a published study stating its basis.
DFDE / TFDE	methaneFraction	Requires administrator data	% CH4 by mass in gas fuel	0–100	Methane mass fraction of the gas actually burned. Depends on cargo composition; requires a cargo document.
ME-GI	dailyGasDemand	Requires administrator data	t LNG-equivalent/day	0–500	Daily LNG-equivalent gas demand for propulsion. Requires vessel-specific shop-test or operator data.
ME-GI	propulsionPower	Requires administrator data	MW	0–100	Installed propulsion power. Requires maker or classification documentation.
ME-GI	loadFactor	Requires administrator data	%	0–100	Average load over the voyage. Requires operator voyage data.
ME-GI	thermalEfficiency	Requires administrator data	%	1–100	Fuel-to-shaft efficiency of the propulsion chain. Requires maker data.
ME-GI	gasShare	Requires administrator data	%	0–100	Share of fuel energy supplied as gas. Requires maker data.
ME-GI	lngLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the LNG actually carried. Depends on cargo composition; requires a cargo document or verified reference value.
ME-GI	pilotShare	Requires administrator data	%	0–20	Share of fuel energy supplied as pilot fuel. Requires maker data.
ME-GI	pilotFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the pilot fuel. Requires a fuel analysis.
ME-GI	auxFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the auxiliary liquid fuel. Requires a fuel analysis.
ME-GI	co2eFactor	Requires administrator data	t CO2e/t fuel	0–10	Well-to-wake or tank-to-wake CO2e factor. Requires a defined regulatory or published source.
ME-GI	methaneSlip	Requires administrator data	% of methane supplied to the engine	0–10	Unburned methane leaving the engine, as a scenario assumption for a specific engine and load — not a universal characteristic of a propulsion type. Requires maker measurement or a published study stating its basis.
ME-GI	methaneFraction	Requires administrator data	% CH4 by mass in gas fuel	0–100	Methane mass fraction of the gas actually burned. Depends on cargo composition; requires a cargo document.
X-DF	dailyGasDemand	Requires administrator data	t LNG-equivalent/day	0–500	Daily LNG-equivalent gas demand for propulsion. Requires vessel-specific shop-test or operator data.
X-DF	propulsionPower	Requires administrator data	MW	0–100	Installed propulsion power. Requires maker or classification documentation.
X-DF	loadFactor	Requires administrator data	%	0–100	Average load over the voyage. Requires operator voyage data.
X-DF	thermalEfficiency	Requires administrator data	%	1–100	Fuel-to-shaft efficiency of the propulsion chain. Requires maker data.
X-DF	gasShare	Requires administrator data	%	0–100	Share of fuel energy supplied as gas. Requires maker data.
X-DF	lngLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the LNG actually carried. Depends on cargo composition; requires a cargo document or verified reference value.
X-DF	pilotShare	Requires administrator data	%	0–20	Share of fuel energy supplied as pilot fuel. Requires maker data.
X-DF	pilotFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the pilot fuel. Requires a fuel analysis.
X-DF	auxFuelLhv	Requires administrator data	MWh/t	1–30	Lower heating value of the auxiliary liquid fuel. Requires a fuel analysis.
X-DF	co2eFactor	Requires administrator data	t CO2e/t fuel	0–10	Well-to-wake or tank-to-wake CO2e factor. Requires a defined regulatory or published source.
X-DF	methaneSlip	Requires administrator data	% of methane supplied to the engine	0–10	Unburned methane leaving the engine, as a scenario assumption for a specific engine and load — not a universal characteristic of a propulsion type. Requires maker measurement or a published study stating its basis.
X-DF	methaneFraction	Requires administrator data	% CH4 by mass in gas fuel	0–100	Methane mass fraction of the gas actually burned. Depends on cargo composition; requires a cargo document.

Related reading: LNG technologies and the LNG glossary.