Energy-efficiency ratings on electronic devices of eight categories will be published at the end of this year and put into force next year, the country's authority of standardization said Wednesday, warning manufactures, importers and exporters involved to be prepared.

The eight categories that will be labeled will include both white goods and office appliances, such as water heaters, electric cookers, fans, variable-frequency air conditioners, computer monitors and copy machines, according to Wang Ruohong, deputy director of resource and environment standardization under China National Institute of Standardization (CNIS).

The energy-efficiency rating label, as a mandatory mark, enables consumers to compare the energy efficiency of domestic appliances on a fair and equitable basis. It also provides incentives for manufacturers to improve the energy performance of appliances.

China first introduced the rating system in 2003, which is determined by the energy consumption and size of the product, from Class 1 to Class 5. Class 1 represents the highest energy-efficiency type. Refrigerators and air conditioners were the first batch of home appliances required to carry a China Energy Label.

Wang said the energy-rating label, which helps consumers to make a green choice and requires manufacturers to apply energy-saving technologies for strengthening competitiveness, is an important measure for the country to hit its energy conservation target, cutting energy intensity by 20 percent from 2006 to 2010.

CNIS figures showed that the labeling system has helped China save 20 billion kWh of electricity since 2003.

The energy-efficiency rating label system works not just for domestic manufactures, but also for importers and exporters in the sector, Wang said.

The newly amended Energy Conservation Law stipulates that imported products on the list of energy-efficiency rating label should be re-rated in the Chinese system.

Meanwhile, CNIS also helps exporters of electric appliances to align themselves with international rating systems. Wednesday, it signed a one-year contract with Intertek to gain international experience of rating.