Construction and transport have become China's largest energy-consuming sectors, according to research released in Beijing on Friday.

A study by Climate Policy Initiative shows energy use in the building sector grew 28 percent from 2005 to 2008 due to rapid urbanization, with carbon emissions rising 25 percent.

Energy consumption in the transport sector also grew 25 percent over the same period and increased rapidly after 2008 due to the 4-trillion-yuan ($608 billion) economic stimulus package, which mainly went to infrastructure construction.

The changes did not hamper China from achieving its goal in the 11th Five-Year Plan (2006-2010) to reduce energy consumption per unit of GDP by 20 percent, said the study report.

"The country reduced its energy consumption per unit of GDP by 19.06 percent at the end of 2010," Wei Jianguo, secretary-general of the China Center for International Economic Exchanges, a high-level business think tank, and former vice-minister of commerce, said on Friday.

However, consumption among the construction and transportation industries will put pressure on future plans, with the primary goal in the 12th Five-Year Plan (2011-2015) to reduce energy usage per unit of GDP by 16 percent, according to Dai Yande, deputy director of the National Development and Reform Commission's energy research institute.

Since 2005, China has reduced carbon dioxide emissions by 1.8 billion tons through increasing energy efficiency, said He Jiankun, director of the State Low-carbon Energy Laboratory.

However, if the country maintains GDP growth of 10 percent and energy efficiency continues to rise at the current rate, by 2015 carbon dioxide emissions in China will reach 10 billion tons, equal to the total for the United States and European Union. "By 2020, the amount will reach 13 billion tons," added He.

The report said further enhancement in energy efficiency in the next five years will also impose higher costs, threatening economic development.

Dai recommended that, besides developing clean energy, China should gradually shift from being the factory of the world to developing its own brand or culture economy.

Su Wei, China's top climate negotiator, also emphasized that the development of low-carbon energy, enhancement of energy efficiency, transition of economic structure and promotion of forest carbon sinks are the country's best solution for saving energy and reducing emissions.

China has contributed much in the fight against climate change and announced it will reduce the intensity of carbon emissions per unit of GDP by 40 to 45 percent by 2020 from 2005 levels.

Climate Policy Initiative assesses, diagnoses and supports national efforts to achieve low-carbon growth, with offices in San Francisco, Berlin, Venice, Beijing and Rio de Janeiro.