The Energy Efficiency Design Index is the design-phase carbon-intensity metric for new ships under MARPOL Annex VI. It pairs with CII on the operational side.
Formula (core case)
The simplified expression used by our calculator, covering single-ME / single-fuel / no-PTO ships:
$$ \text{EEDI}\text{attained} = \frac{\sum_i P{\text{ME},i} \cdot C_{f,\text{ME}} \cdot \text{SFC}_\text{ME}
- P_\text{AE} \cdot C_{f,\text{AE}} \cdot \text{SFC}_\text{AE}
- \text{Innovative credit}} {\text{Capacity} \cdot V_\text{ref}} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\text{EEDI}_\text{attained}$ | Attained Energy Efficiency Design Index | g CO₂ / (t·nm) | result |
| $P_{\text{ME},i}$ | 75 % of MCR of main engine $i$ | kW | design data |
| $C_{f,\text{ME}}$ | Fuel-to-CO₂ factor for main-engine fuel | t CO₂ / t fuel | MEPC.364(79) |
| $\text{SFC}_\text{ME}$ | Main-engine specific fuel consumption at reference load | g / kWh | NOx Technical File |
| $P_\text{AE}$ | Auxiliary-engine power | kW | MEPC.231(65) §2.5.6 |
| $C_{f,\text{AE}}$ | Fuel-to-CO₂ factor for auxiliary-engine fuel | t CO₂ / t fuel | MEPC.364(79) |
| $\text{SFC}_\text{AE}$ | Auxiliary-engine specific fuel consumption | g / kWh | NOx Technical File |
| $Innovative credit$ | CO₂ saving from Category B/C energy-saving technologies | g CO₂ / h | MEPC.1/Circ.815 |
| $Capacity$ | DWT (cargo) or GT (passenger / cruise) | t or - | MEPC.328(76) Table 1 |
| $V_\text{ref}$ | Design speed at 75 % MCR on design draft | kn | sea-trial / tank test |
Required EEDI
$$ \text{EEDI}_\text{required} = a \cdot \text{Capacity}^{-c} \cdot (1 - Z) $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\text{EEDI}_\text{required}$ | Required Energy Efficiency Design Index | g CO₂ / (t·nm) | result |
| $a$ | Ship-type reference-line coefficient | - | MEPC.328(76) Table 1 |
| $c$ | Ship-type reference-line exponent | - | MEPC.328(76) Table 1 |
| Capacity | DWT or GT depending on ship type | t or - | MEPC.328(76) Table 1 |
| $Z$ | Phase reduction factor - Phase 0 = 0, Phase 1 ≈ 10 %, Phase 2 = 20–30 %, Phase 3 = 5–50 % | fraction | MEPC.328(76) |
Compliance margin
$$ \text{Margin %} = \frac{\text{Required} - \text{Attained}}{\text{Required}} \times 100 $$
Positive = ship is better than required (compliant). Negative = over the limit, non-compliant without further design changes or innovative-tech credits.
Innovative-technology credits
Per MEPC.1/Circ.815, energy-saving technologies can be grouped into three categories:
- Category A - technologies that reduce energy used on board (e.g. efficient hull coatings). Credit in the denominator via the $(1-w)$ term (not in v1).
- Category B - technologies that generate electrical energy (e.g. shaft generators, waste-heat recovery). Credit subtracted from the numerator.
- Category C - technologies that reduce propulsion power (e.g. wind assist, air lubrication). Credit subtracted from the numerator with an availability factor $f_\text{eff}$.
Our v1 calculator exposes a single “Innovative-tech credit” input in grams CO₂/h that you can use to experiment with totals; the full per-category treatment is a Phase 1B refinement.
What v1 does NOT include
Load these into Phase 1B as refinements:
- PTI / shaft-generator terms - dual flow of electrical power between ME and aux.
- Full $f_j$ (ice class), $f_i$ (cubic capacity), $f_w$ (weather), $f_c$ (chemical tanker), $f_m$ (ship-specific) correction factors.
- Phase 3 per-size-band reduction table - currently we default to the ship-type value; the full table has further size-band breakdowns.
- EEXI - uses the same formula but with a 75 %-MCR reference speed derived with power limitation. Coming as calculator #6.
Sources
- IMO Resolution MEPC.328(76) - revised MARPOL Annex VI including Phase 3.
- IMO Resolution MEPC.231(65) - 2013 Guidelines for reference lines.
- IMO Resolution MEPC.364(79) - Cf fuel conversion factors.
- IMO Circular MEPC.1/Circ.815 - innovative-technology categories.
- IMO Resolution MEPC.203(62) - original EEDI amendments (2011).