A SEEMP Part III implementation plan typically combines several operational measures (slow steaming, weather routing, hull cleaning, trim optimisation, just-in-time arrival, fuel switching, energy-saving devices). The total fuel saving from a stack of measures is calculated using the standard non-overlapping multiplicative formula, on the assumption that the measures act on the same baseline fuel consumption with no double-counting.
Combined-savings formula
$$ \text{Combined saving} = 1 - \prod_{i} (1 - s_i) $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $Combined saving$ | Combined fractional fuel saving from all measures | fraction | result |
| $s_i$ | Fractional fuel saving from measure $i$ | fraction | IMO MEPC.346(78) typical ranges |
| $\prod_i$ | Product over all measures $i$ | - | mathematical operator |
Annual fuel saved
$$ F_\text{saved} = F_\text{baseline} \cdot \text{Combined saving} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $F_\text{saved}$ | Annual fuel saved | t / yr | result |
| $F_\text{baseline}$ | Baseline annual fuel consumption | t / yr | IMO DCS report |
Annual CO₂ saved
$$ m_{\text{CO}2,\text{saved}} = F\text{saved} \cdot C_f $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $m_{\text{CO}_2,\text{saved}}$ | Annual CO₂ saved | t CO₂ / yr | result |
| $C_f$ | CO₂ conversion factor for the relevant fuel | t CO₂ / t fuel | MEPC.364(79) Table 1 |
For HFO the default Cf is 3.114 t CO₂ / t fuel; for MGO/MDO 3.206; for LNG 2.750 (excluding methane slip). Use fuel-specific Cf for non-HFO fuel mixes; use the LNG well-to-wake calculator for full lifecycle analysis.
Annual cost saving
$$ \text{USD}\text{saved} = F\text{saved} \cdot P_\text{bunker} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\text{USD}_\text{saved}$ | Annual cost saving | USD / yr | result |
| $P_\text{bunker}$ | Bunker price | USD / t fuel | market price |
Typical industry savings ranges
| Measure | Typical saving range |
|---|---|
| Slow steaming (10% speed reduction) | 8 to 15% |
| Weather routing (long-distance ocean) | 2 to 5% |
| Hull cleaning + propeller polishing | 5 to 8% |
| Trim optimisation software | 1 to 4% |
| Just-in-time arrival | 2 to 7% |
| Energy-saving devices (PBCF, ducts, pre-swirl stators) | 2 to 5% |
| Fuel switching (B30 biofuel blend) | ~30% CII improvement |
| Fuel switching (B100 / bio-MGO) | ~95% CII improvement |
| Cargo heating optimisation | 1 to 3% |
| Shaft generator + waste heat recovery | 1 to 4% |
Sources
- IMO Resolution MEPC.346(78) - 2022 Guidelines for the Development of a Ship Energy Efficiency Management Plan (SEEMP).
- IMO Resolution MEPC.328(76) - Amendments to MARPOL Annex VI introducing SEEMP Part III.
- IMO Resolution MEPC.364(79) - Cf fuel conversion factors.
- ICS SEEMP Guide (4th edition, 2023).
- BIMCO CII Clause for Time Charters (November 2022).
- DNV Maritime Forecast to 2050 (2025 edition).
See also
- Wiki: SEEMP I, II and III.
- Wiki: Slow steaming and CII.
- Wiki: What is CII.
- Wiki: MARPOL Annex VI.
- CII attained calculator.
- Engine cube-law fuel calculator - speed-fuel relationship for slow steaming.