"IEA's data on China's energy use is unreliable," Zhou Xian, an official with China National Energy Administration said Tuesday at a news conference, state-owned news agency Xinhua reports.
The IEA study indicates that China consumed 2.252 billion tons of oil equivalent in 2009, which is 4 percent more than United States' 2.17 billion tons.
But a February report from China's National Bureau of Statistics indicates that China's energy consumption last year was 3.1 billion tons of standard coal equivalent, which was equal to 2.132 billion tons of oil equivalent.
An NEA official told Xinhua that the discrepancy in results was because the two agencies had collected data from different sources.
While China refuses to accept its energy-use status, IEA's analysis is on target with its 2007 prediction that China would overtake the United States in energy use and become the world's largest consumer of energy by about 2010.
Even in announcing China's rise to the top ranking, IEA noted, "For those who have been following energy consumption trends closely, this does not come as a surprise."
However, the ascent came faster than expected, IEA said, because China was much less affected by the global financial crisis than the United States.
Further, the IEA now predicts that China will account for 40 percent of overall growth in energy demand over the next 20 years.
"This will have major implications for the global energy system, energy production and the environment," said IEA economist Fatih Birol, Canada's Financial Post reports.
In order to meet the country's surging demand for energy, Birol said China is likely to build as many power plants in the next 15 years as did the United States over 60 years.
NEA's Zhou said in his news conference that IEA lacked understanding about China's efforts to cut energy use and emissions, particularly the country's aggressive expansion of new energy development.
But in a statement on its Web site, IEA pointed out that China's current energy demand would be even higher if the government had not made progress in reducing the energy intensity (the energy input per dollar of output) of its economy.
"It has also very quickly become one of the world's leaders in renewable energy, particularly wind power and solar energy, and paved the way for a big expansion of nuclear power," IEA said.