The Empire State Building, which has been undergoing a $20m energy saving retrofit, today announced that it would meet all its electricity needs through wind power.

In a two-year deal, the building will buy 55m kilowatt hours worth of renewable energy certificates a year – the equivalent of its annual energy needs – from the Texas-based Green Mountain Energy Company.

That is more than double the amount of renewable power purchased by any other commercial customer in New York City, the announcement said.

It said reductions in carbon emissions from the shift to wind power for the 102-storey building were the equivalent of turning off the lights in nearly every house in New York State for a week.

Tony Malkin, the president of Malkin Holdings, which runs the Empire State, dismissed the idea that he had set out to "green" the building, noting that Green Mountain had come in with the lowest bid to supply power.

"Everything we are doing at the Empire State building is based on the market price, demonstrating you can have efficiency at the same or at lower cost," he said.

The building, constructed in the throes of the Great Depression 80 years ago, reigned for more than 40 years as the tallest building in New York. Following the destruction of the World Trade Centre in the 9/11 attacks, it is again the tallest in the city.

But in recent years, its grandeur had faded, and in 2009 Malkin undertook a $550m renovation project including the energy retrofit.

During the rehab, workers installed smart controls for heating and cooling, and stripped out the building's 6,500 windows to add insulating films.

Some environmental groups have questioned whether renewable energy certificates represent a true reduction in carbon emissions, short of compelling companies to build new wind power plants to meet increased demand.

But Malkin argued there was a strong symbolic value of having the Empire State shift to wind energy.

"There is no way to be certain that the power I paid for actually shows up at my building, but it certainly displaces other power that is not green," he said.

"I am persuading an economic incentive for people to promote more clean power, and I am causing people to think: 'Gee, should I really be investing in the manufacture of non-clean power?'"