Caithness Long Island Energy has received a state grant that allowed for modifications to its 350-megawatt power plant to reduce CO2 emissions by 4,000 tons a year, the company said.

The modifications, completed in December, further cut emissions from what the company said is the island’s most efficient gas-fired power plant. The grant, from the New York State Energy Research and Development Authority, is part of a statewide plan to reduce emissions from traditional plants.

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NYSERDA spokesman Peter Constantakes said the $163,000 award, the result of a competitive bid, came from NYSERDA’s Power Generation Competitive Greenhouse Gas Reduction Pilot Program. It’s part of Gov. Andrew M. Cuomo’s Reforming the Energy Vision initiative, which seeks to cut greenhouse gas emissions by 80 percent from 1990s levels by 2050.

In a statement, Caithness said the CO2 reductions were achieved by upgrading to more technically advanced turbine components, resulting in more efficient use of the plant’s natural-gas fuel. Spokesman Don Miller wasn’t available to say whether customers would see lower costs as a result of that increased efficiency.

The plant’s owners have a $1.676 billion, 20-year contract with LIPA.

Caithness said its 350-megawatt plant produces more energy than other power units on Long Island because its efficiencies make its power among the least expensive on-island resources, more so than antiquated National Grid-owned power plants that have higher capacity ratings but are used less.

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Caithness said lower emissions from the plant have saved ratepayers $7.8 million in emission credit costs since it opened in August 2009. LIPA pays around $75 million a year in capacity costs for the plant.