Calculation Examples

Below an example is provided of an ESI calculation for a specific ship. The ship in the example has one main engine and three auxiliary engines. The ship uses HIGH, MID and LOW categories fuel oil and reports on fuel consumed and distance sailed; no efficiency increase has yet been established.


For the formulas and baselines see ‘ESI Formulas’ and ‘IMO annex Regulations and ESI Baselines’.

Nitrogen oxides ESI NOx


Main engine(s) Auxiliary engine(s)
NOX Limit Value 17 11.5 g/kWh
NOX Rating 15 11 g/kWh
Δ Emission 2 0.5
Rated Power 9480 970 kW
Number of engines 1 3

Calculation of the NOx sub points {(17 – 15) x 9480/17 + (11.5 – 11) x 970 x 3/11.5} x 1/(9480 + 970 x 3) x 100 = 1241 x 0.008 = 10.0

This results in an ESI NOx of (10 x 2)/3 = 6.67



Sulphur oxides ESI SOx


The average sulphur content of the different fuels is extracted from the bunker delivery notes. The average for the respective fuels is the weighted average over all bunkers.

HIGH MID LOW
Baseline 3.50 0.50 0.10 % S (m/m)
Actual 2.00 0.40 0.05 % S (m/m)

For the different fuels, the relative improvement compared to the baselines is calculated; see also ‘ESI formulas’ and ‘IMO annex regulations and ESI baselines’

Calculation of the SOx sub points (3.50 - 2.00) / (3.5 – 0.5) x 30 + (0.50 - 0.40) / (0.5 - 0.1) x 35 + (0.10 - 0.05) / (0.1 - 0.0) x 35 = 15.0 + 8.75 + 17.5 = 41.25

The resulting ESI SOx is 41.25/3 = 13.75



Energy Efficiency Operational Indicator ESI CO2


Ships may choose to report on two of the EEOI data sets viz. fuel consumption and distance sailed; the data provided should be as described in the definitions section of the Guidelines for Voluntary Use of the Ship Energy Efficiency Operational Indicator (MEPC.1/Circ.684). The reporting period for the two data sets should coincide with the reporting period for the BDNs of the ship. Supply of data on the type of cargo and/or the value of the EEOI is not requested.

Reporting (every half year) of fuel and distance will give an ESI CO2 of 5 while an efficiency increase in % in the reporting period over the base line period is added as points; the total is capped at 15.

ESI Score


For this example the respective values lead to an ESI Score of

6.67 + 13.75 +5 = 25.42

The presence on this ship of OPS would add 10 points and the following ESI Score:

6.67 + 13.75 +5 + 10 = 35.42