Most Emission-Efficient Gas Carriers
Ships ranked by AER (Annual Efficiency Ratio) — grams of CO₂ emitted per tonne of deadweight carried one nautical mile (g CO₂/dwt·nm), the IMO carbon-intensity metric behind the CII rating — from official EU MRV emissions data for reporting year 2025. Lower is greener. Pick a segment and size class to see the greenest vessels first.
| # | Vessel | Size (DWT) | Built | Carbon intensity — AER (g CO₂/dwt·nm) | Grade |
|---|---|---|---|---|---|
| 1 |
AL SHELILA
IMO 9965423
|
93,640 | 2024 |
4.6
|
A |
| 2 |
ARISTARCHOS
IMO 9862918
|
93,427 | 2021 |
5.0
|
A |
| 3 |
ASTERIX I
IMO 9892298
|
93,403 | 2023 |
5.1
|
A |
| 4 |
PERTAMINA GAS DAHLIA
IMO 9937074
|
58,265 | 2024 |
5.2
|
A |
| 5 |
HELLAS BLISS
IMO 9989649
|
55,711 | 2025 |
5.2
|
A |
| 6 |
ASSOS
IMO 9957725
|
93,771 | 2024 |
5.4
|
A |
| 7 |
PERTAMINA GAS CASPIA
IMO 9937062
|
58,257 | 2024 |
5.5
|
A |
| 8 |
HANNIBAL
IMO 9933523
|
58,000 | 2024 |
5.5
|
A |
| 9 |
HARZAND
IMO 9922768
|
57,975 | 2023 |
5.5
|
A |
| 10 |
NILE RIVER
IMO 9933779
|
58,666 | 2024 |
5.5
|
A |
| 11 |
PHOENIX HARMONIA
IMO 9947483
|
56,711 | 2023 |
5.6
|
A |
| 12 |
TRAIANO KNUTSEN
IMO 9854765
|
96,354 | 2020 |
5.6
|
A |
| 13 |
ADAMASTOS
IMO 9879698
|
93,566 | 2021 |
5.6
|
A |
| 14 |
OCEANUS AURORA
IMO 9555008
|
58,495 | 2023 |
5.7
|
A |
| 15 |
ARISTIDIS I
IMO 9862906
|
93,368 | 2021 |
5.7
|
A |
| 16 |
HYPERION
IMO 9922770
|
57,984 | 2023 |
5.7
|
A |
| 17 |
ATTALOS
IMO 9862920
|
93,321 | 2021 |
5.7
|
A |
| 18 |
LUPINUS PLANET
IMO 9929209
|
55,091 | 2022 |
5.8
|
A |
| 19 |
ITHACA GAS
IMO 9987550
|
56,457 | 2025 |
5.8
|
A |
| 20 |
LEGISLATOR
IMO 9938523
|
59,017 | 2022 |
5.9
|
A |
| 21 |
AQUAMARINE PROGRESS II
IMO 9947495
|
56,805 | 2024 |
5.9
|
A |
| 22 |
ASKLIPIOS
IMO 9884021
|
93,352 | 2021 |
5.9
|
A |
| 23 |
LOGAN EXPLORER
IMO 9941233
|
54,994 | 2023 |
6.0
|
A |
| 24 |
COPERNICUS
IMO 9706516
|
54,656 | 2015 |
6.0
|
A |
| 25 |
ROBERTO
IMO 9839727
|
55,239 | 2020 |
6.0
|
A |
| 26 |
LANTANA PLANET
IMO 9933444
|
55,153 | 2023 |
6.1
|
A |
| 27 |
DANUBE RIVER
IMO 9933767
|
58,666 | 2023 |
6.2
|
A |
| 28 |
TP PERSEVERANCE
IMO 9730139
|
54,669 | 2015 |
6.2
|
A |
| 29 |
APOSTOLOS
IMO 9957737
|
93,658 | 2021 |
6.2
|
A |
| 30 |
BW VAR
IMO 9748227
|
54,053 | 2016 |
6.2
|
A |
| 32 |
GAS JUSTESEN
IMO 9940992
|
55,076 | 2023 |
6.2
|
A |
| 31 |
CLERMONT
IMO 9706487
|
54,543 | 2015 |
6.2
|
A |
| 33 |
VIVIT DUBHE
IMO 9835173
|
54,406 | 2019 |
6.3
|
A |
| 34 |
PASCO MARSEL
IMO 9939204
|
29,991 | 2023 |
6.3
|
A |
| 35 |
BW GEMINI
IMO 9703007
|
54,116 | 2015 |
6.3
|
A |
| 36 |
G. FOREVER
IMO 9409302
|
54,800 | 2008 |
6.4
|
A |
| 37 |
BW MESSINA
IMO 9735062
|
54,647 | 2017 |
6.4
|
A |
| 38 |
BW POLARIS
IMO 9901984
|
58,312 | 2022 |
6.4
|
A |
| 39 |
AMORE MIO I
IMO 9943841
|
82,076 | 2023 |
6.4
|
A |
| 40 |
GALAXY RIVER
IMO 9670016
|
54,081 | 2014 |
6.4
|
A |
| 41 |
REFERENCE POINT
IMO 9832808
|
55,427 | 2020 |
6.4
|
A |
| 42 |
GAS TIFFANY
IMO 9726085
|
54,702 | 2016 |
6.4
|
A |
| 43 |
DURHAM
IMO 9889564
|
55,408 | 2021 |
6.5
|
A |
| 44 |
BW CAPELLA
IMO 9901996
|
58,243 | 2022 |
6.5
|
A |
| 45 |
CLIPPER EXPLORER
IMO 9852949
|
50,513 | 2019 |
6.5
|
A |
| 46 |
VEGA SUN
IMO 9793258
|
50,591 | 2017 |
6.5
|
A |
| 47 |
CONTINENTAL
IMO 9714381
|
54,490 | 2015 |
6.6
|
A |
| 48 |
BW FRIGG
IMO 9733337
|
54,053 | 2016 |
6.6
|
A |
| 49 |
ORIENTAL KING
IMO 9804253
|
54,373 | 2017 |
6.6
|
A |
| 50 |
VIVIT THUBAN
IMO 9840867
|
50,703 | 2019 |
6.6
|
A |
Which engines power the greenest fleets?
The main engine is the single largest CO₂ source on board — typically well over 80% of a ship's emissions come from propulsion. We aggregated this ranking the other way around: every engine design is scored by the measured carbon intensity of the vessels carrying it, licensee-built units merged under their design brand. The verdict from the 2025 data — modern dual-fuel designs like MAN B&W's ME-GI and WinGD's X-DF families, together with EGR/SCR-abated and ultra-long-stroke G-type engines, consistently power the most emission-friendly ships in service.
AER (Annual Efficiency Ratio) = annual CO₂ emissions ÷ (deadweight × distance sailed), the IMO carbon-intensity metric used for CII ratings. It is built only from measured CO₂, distance and deadweight — not the self-reported cargo transport-work figure, which is unreliable. Implausible outliers (top 2% per segment) are excluded. Grade A–E reflects each vessel's rank within its segment. Source: EMSA THETIS-MRV.