The core measure for comparing the relative efficiency of the world’s fleet is grams of CO2 per tonne per nautical mile.
RightShip utilise one of two sources when determining an individual vessel’s efficiency:
- EEDI: Energy Efficiency Design Index – measures the theoretical CO2 emission performance of new ships over 400 gross tonnes and is calculated from ship design and engine performance data. This is a regulatory requirement for new ships developed by the IMO (and applied on an ad-hoc basis to existing vessels)
- EVDI: Existing Vessel Design Index – Developed by RightShip, also measures a ship’s theoretical CO2 emissions per nautical mile travelled. However, the EVDI can be applied to existing vessels as well as new builds (where EEDI is not available/applicable).
As the two methods compare relative efficiency on the same basis, a like-for-like comparison of efficiency is achievable – as outlined in DNVGL’s review of RightShip’s methodology in 2015 (see below).