Spend any time online, looking up information on cruise ships, and you'll find dozens of articles lambasting them as inefficient, wasteful energy hogs.

My personal jury is still out on that question (after all, you have to consider that when 3,000 passengers and 1,500 crew are on a ship for a week, that's a few thousand cars that won't be on the road, and many tons of household waste that won't be generated), but I'm fully onboard with the idea that cruise lines should be doing everything they can to reduce their carbon footprint. And some cruise lines are: Over the past decade, many have invested heavily in improving efficiency, reducing waste, and beefing up their recycling practices -- both because that helps their bottom lines and because, in our increasingly green-conscious world, being on the green side reaps reputational benefits.

There are, of course, many different ways of measuring environmental impact, and, for a vessel as complex as a modern cruise ship, literally hundreds of factors need to be taken into consideration -- from the shape of the hull and the efficiency of the engines, to the type of fuel used and the systems used to treat wastewater, to less obvious things like the way developing chemicals used by the ship's photographers are recycled and disposed of.

The list goes on and on, but if you want to make a start, and pick a ship in part based on its relative efficiency, you have a new tool to work with: In December 2010, a website called ( went live, rating the efficiency of the world's oceangoing ships, raising awareness, and thereby promoting the development of more efficient vessels.

The site was created by the Carbon War Room (, a not-for-profit organization founded by Sir Richard Branson and a group of high-level business and investment muckety-mucks, with the goal of promoting entrepreneurial, market-driven solutions to climate change. Cruise ships represent only a tiny percentage of the more than 60,000 vessels on the site, the vast majority of them container ships, tankers, bulk carriers, cargo ships, and ferries.

While sorting through the site's ratings for nearly all the midsize and large cruise ships out there, I found that the results were pretty interesting -- and also a bit suspect in places.

How It Works rates ships on an A-to-G scale, with A being the best and G being not so good. The ratings are based on the Energy Efficiency Design Index (EEDI) developed by the International Maritime Organization's Marine Environment Protection Committee as a measure of ships' relative CO2 emissions, based on the efficiency of their design and engine performance. In coming up with its A-to-G ratings, applied a curve so that only vessels of similar size and type (container ships, bulk carriers, cruise ships, various types of tankers, etc.) are compared.

Questions & Anomalies

In my examination of the site's ratings, I noted several anomalies. For instance, there were several cases in which sister ships built on the same design, just a year or so apart, received radically different scores. says that this can be explained by the fact that the EEDI is based on numerous parameters, and "if even one of those differs between sister ships they could get a different EEDI, which could then push them into a different rating bracket."

So they say, but that doesn't quite settle my doubts. As a prime example, Celebrity Cruises' four Millennium-class ships -- Celebrity Constellation, Celebrity Infinity, Celebrity Millennium, and Celebrity Summit -- get ratings of F, B, E, and F, respectively. The outlier "B" score for Infinity appears to be a matter of typographical error in the EEDI (Size) Rating, which as listed is vastly different for Infinity than for her sister ships, though all four are in fact of identical gross tonnage and passenger capacity. Similarly, sister ships Norwegian Gem and Norwegian Jade are rated C and F, respectively, with the size rating appearing to be the determining factor in the variance -- though again, the two ships are exactly the same size.

Far be it from me to kvetch about typographical errors (if that's what they are), especially when I agree wholeheartedly with ShippingEfficiency's goal of stimulating the development of more efficient vessels. But, in the absence of other data (or of a response from, which has not yet returned an answer to my questions), I have to note my grain-of-salt suspicion about the ratings' absolute reliability.

Qualms aside, here's a rundown of the big winners, along with a few interesting tidbits.

The A List

Cruise ships receiving a top-level A score from were:

  • Cunard's Queen Mary 2, which was not a surprise, since she was designed to really slice through the water on hard transatlantic runs, despite her huge size.
  • MSC's MSC Fantasia and MSC Splendida, heading up what was the best across-the-board performance for any one cruise line.
  • Princess's Diamond Princess and Crown Princess, though not Sapphire Princess (an identical sister to Diamond) and Emerald and Ruby Princess (sisters to Crown).
  • Celebrity's Celebrity Century, the oldest ship in the Celebrity fleet, outpacing even the newer (and allegedly very efficient) Solstice-class ships, as well as her sister ship, Celebrity Mercury.
  • Royal Caribbean International's Majesty of the Seas and Monarch of the Seas, the oldest ships currently sailing in the RCI fleet.

The B-List

The ships that leap out among those with a B rating are Royal Caribbean's Oasis of the Seas and Allure of the Seas, co-holders of the "World's Largest Cruise Ship" distinction. Oasis and Allure scored higher than any of the other, much smaller Royal Caribbean ships, aside from those mentioned above.

Other ships garnering a B rating were:

  • Carnival's Freedom, Triumph, and Valor
  • Celebrity's Infinity
  • Costa's Allegra, Classica, and Romantica
  • Crystal's Serenity
  • MSC's Magnifica, Musica, Orchestra, and Poesia
  • Princess's Star Princess
  • Star Clippers' Star Clipper

Of Interest

  • As noted above, MSC Cruises posted the most consistently high scores among the cruise lines, with two of its ships receiving A's and four receiving B's. Four others -- the line's older, midsize Lirica, Opera, Armonia, and Sinfonia -- received D ratings.
  • Azamara Club Cruises, a line I like quite a bit otherwise, performed worst among all the lines, with its two ships, Azamara Journey and Azamara Quest, both receiving dismal G ratings. Oceania Cruises' original three vessels, Regatta, Insignia, and Nautica, which are identical to Azamara's ships in their construction (all of them having originally been part of the Renaissance Cruises fleet), received F ratings.
  • Most other lines were all over the map, some in a consistent way (the majority of Holland America's ships scored as D's, with a few C's and a single G mixed in), others with substantial variation (Royal Caribbean had ships score in every one of the ratings levels, from A to G).

Scores for most cruise vessels (save many of the smaller ones) are available through ShippingEfficiency's Vessel Search function, though you have to register for the site to use it. Registration is free of charge.