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(1:34 p.m. EDT) -- Carnival Corporation & plc, the parent company of Carnival Cruise Lines, Holland America Line and Princess Cruises, among others, has improved its fuel efficiency by 24 percent from 2007 through 2014, resulting in a savings of $2.5 billion in fuel costs for the company.

The improved efficiency is a result of the company's multiyear Fleet Fuel Conservation Program, which combines energy-savings programs onboard ships with energy-efficient designs created to reduce energy consumption.

"Environmental stewardship is vital to our relationship with ports and the communities where we do business, and it's the right thing to do," Thomas M. Dow, vice president, public relations, Carnival Corp., said at a National Press Club event celebrating world tourism in Washington D.C.

Among the areas the company has targeted over the past seven years are:

Propulsion: Improving how ships move through water by optimizing ship speeds and the distance between ports to create fuel-efficient itineraries.

Hull coatings: New hull coatings and cleaning technologies minimize the growth of marine organisms that can create a drag on ships, thereby reducing the amount of fuel needed to propel ships.

Air-conditioning: Carnival has installed energy-efficient air-conditioning systems onboard its ships. The systems are the second-largest consumer of onboard energy after propulsion.

Lighting: The company is in the process of replacing 4 million traditional lights with energy-efficient LED bulbs.

Carnival estimates that by the end of 2014 it will have saved more than 1 billion gallons of fuel, thereby reducing the carbon emissions of its 100-ship fleet by 12 billion kilograms over a seven-year period.

In September 2013, Carnival announced it would spend upwards of $400 million on testing and installing emission filtration and scrubbing devices on more than 70 percent of its fleet.

--By Dori Saltzman, News Editor