A partnership between the Port of Seattle, two major cruise lines (Princess Cruises and Holland America Line) regulators and industry has resulted in important emissions reductions while vessels berth. Simply by “plugging in” to the city grid and turning off their engines, participating vessels are cutting annual CO2 emissions by up to 29% annually, with financial savings of up to 26% per call. This simple practice has great scope for expansion.

What is it?

When a vessel plugs in to the city grid, the vessel's diesel engines are shut down, eliminating the emissions from the ship. This process also referred to as “cold ironing”. Without shore power, the vessel's diesel engines would be running continuously to provide power for onboard equipment such as lighting, pumps, ventilation, and communication required for operations at berth, or “hotelling”. Cold ironing is an effective way of reducing emissions from vessels at berth. Emissions of oxides of nitrogen (NOx), particulate matter (PM), hydrocarbon (HC), and carbon dioxide (CO2) emissions are eliminated when a vessel goes cold.

The Port of Seattle has been working closely with the maritime community on voluntary, collaborative approaches to reducing emissions. In an effort to strengthen these efforts, the Port initiated and is leading the Puget Sound Maritime Air Forum, a voluntary public/private partnership working for healthy air and maritime trade. The Princess Cruises and Holland America Line shore power projects are two examples of successful collaborative projects at the Port of Seattle. Both projects were initiated, funded, and implemented by the cruise lines with the support of the Port and agency partners, the U.S. EPA and Seattle City Light.

How does it work?

Shore power, also known as "cold ironing," enables ships to turn off their diesel engines and connect to local electric power that travels to the ship from a specially designed transformer at the dock. As a result, shore-based electricity runs all onboard services during the day-long calls.

Princess Cruises and Holland America Line have outfitted ships with custom-built, state-of-the-art electrical connection cabinets that automatically connect the ship's electrical network to the local electrical network ashore.

The electrical power is transmitted from the landside transformer to the vessel via four 3 1/2-inch diameter flexible electrical cables. The actual cable connection on the vessel is a traditional, though quite large, male/female plug and socket. Shore power works at Terminal 30 because:

Cruise vessels call frequently (i.e. one day per week) during the cruise season (May 1st to September 30th annually)

  • Cruise vessels have a high hotelling load (typical power load is 7-12 MW), which is much higher than cargo vessels
  • Electrical infrastructure in place from previous use as a container terminal
  • Interruptible power arrangement creates a lower cost per kilowatt than non-interruptible power, and makes the option more affordable for the cruise industry. The primary power source in the Pacific Northwest is hydropower.

Princess Cruises and Holland America Line vessels have been modified to connect to shore power at the Port of Seattle Port's Terminal 30, both to reduce air emissions and fuel consumption. Princess Cruises has modified 7 vessels to use shore power in Seattle and Juneau. Holland America's Vista-class cruise ships ms Westerdam and ms Oosterdam were modified in 2006; in early 2007, ms Noordam was similarly modified to accept shore-power. Both cruise lines will buy and use electricity provided by Seattle City Light, instead of burning ship-board fuels for power while calling to the Port of Seattle.

CO2 emissions reductions

Combined emissions reductions for Princess Cruises in 2005 & Holland America Line in 2006 are 3,525t CO2e:

Princess Cruises: In 2005, the equivalent of 2,735 tons of CO2 emissions was eliminated by Princess' use of shore power while calling to the Port of Seattle Terminal 30 Cruise Facility.
Holland America: In 2006, the ms Westerdam and ms Oosterdam each made 21 calls to the Port of Seattle Terminal 30 Cruise Facility. As the shore power was still being completed and tested during the first part of the 2006 cruise season, only 7 calls by the ms Oosterdam and 8 calls by the ms Westerdam utilized the shore power infrastructure during the entire call. CO2 emissions per call without shore power are equal to 95.2 tons; with shore power the CO2 emissions are equal to 8.2 tons. In 2006, Holland America Line's use of shore power at the Port of Seattle Terminal 30 Cruise Facility eliminated an estimated 789.6 tons per year of CO2. That's a 29% reduction in CO2 emissions
The emissions benefits were calculated using an "activity-based" approach - for ocean-going vessels this is calculated by hours used, engine specifics, fuel type, engine load factors, and emission factors. These were calculated for the Puget Sound Maritime Air Emission Inventory, which is a 2005 baseline of all maritime-related activity in the entire Puget Sound airshed. The emissions benefits come from not using the engines to generate power (thus reducing fuel consumption). You can find more specifics on how the activity-based inventory was calculated in the full report at: DEAD LINK

Energy efficiency

Shore power changes the source of energy for the ship engines, but does not affect energy efficiency.



$7.5 million from cruise lines ($2.7 million from Princess Cruises and $4.8 million from Holland America Line). U.S. EPA and Puget Sound Clean Air Agency who provided $75,000 in grant funding to assist with the costs of the project ($50,000 for Princess Cruises and $25,000 for Holland America Line).

Princess Cruises

Total cost of the Princess Cruises shore power project at Port of Seattle was $2.7 million:

  • Landside infrastructure costs were $1.7 million;
  • Shipside retrofit costs were $1 million ($500,000 per vessel)
  • Running costs were $5,140.00 per call
  • Currently, electricity in the Pacific Northwest cost less than marine fuel per hours of use. During the 2007 cruise season, Princess Cruises expects to spend $216,000 to operate shore power at Terminal 30. $106,000 of this expense is for electricity and $110,000 is for set-up, testing, and electrician labor to connect the vessels.

Holland America

Total cost of the Holland America Line shore power project at Port of Seattle was $4.8 million, all of which was paid for by Holland America Line:

  • Landside infrastructure costs were $1.5 million
  • Shipside retrofit costs were $3.3 million ($1.1 million per vessel).
  • The ms Oosterdam and ms Noordam consume about 63 mega-watts of electrical power while hotelling (for approximately an 8 hour port call). Currently, electricity in the Pacific Northwest costs less than marine fuel (per hour of use). The average cost of a mega-watt of electricity in 2006 was approximately $53.50; total cost of electricity per call is $3,371. In comparison, the ms Oosterdam and ms Noordam each consume 12.5 tons of fuel while hotelling, at a cost of $365 per ton or $4,563 per call.
  • By using shore power, Holland America Line saves approximately $1,192 (or 26%) from operating costs per call. Annual savings per cruise season (May 1st through September 30th) is approximately $50,064
  • Running costs are - $3,371.00 per call

Next steps

The Port of Seattle is currently evaluating the relocation of cruise operations at Terminal 30 to Terminal 91 at the north end of Elliott Bay; Terminal 30 will be reactivated as a container terminal facility. Shore power capabilities for cruise ships will be included in the Terminal 91 redevelopment and power will be provided by Seattle City Light.


  • Both cruise lines began planning the projects in the early fall (which is the end of the cruise season in Seattle) for completion and implementation the following cruise season (May 1st to September 30th annually).
  • Once the shoreside infrastructure and vessel modifications were complete, the systems were tested with the vessels connected - this is something that must occur every year, primarily because the vessels that call Port of Seattle change each year.
  • The time and cost may be substantially greater depending on how much infrastructure must be built or redeveloped, especially if the utility line(s) needed are not in close proximity to the terminal, and configuration of the vessel. Time and cost estimates should be developed based on the specifics for each terminal being considered.
  • Frequency of calls needs to be considered in the project cost. For cruise operations, vessels call one day per week for the duration on of the cruise season. For cargo operations, a shipping line may call frequently to a port, but specific vessels do not call frequently and can be reassigned to a different route depending on cargo volumes. This is an important factor in the cost effectiveness of shore power for cargo vessels. If a vessel only calls 2-3 times per year, shore power is not a cost effective strategy for reducing ocean-going vessel emissions at a port.