The law, the first of its kind in China, will require all new residential buildings with fewer than 12 storeys to install solar powered water heating systems, the China Daily reported.

Taller buildings have been exempted due to technological limitations that cannot guarantee 24-hour hot water supply, it said.

"It's an important law that will ensure the wider application of solar power in the city, a sign the government is putting more emphasis on renewable resources," Gao Erjian, a Shenzhen Construction Bureau official, told the paper.

The law was announced this week and will take effect from November, the paper said.

By 2010, half of the new buildings in the economic power house that neighbors Hong Kong will have solar water heating systems, while 20 percent of them will use solar power for generating electricity, it said.

China is now the second-biggest consumer of electricity in the world after the United States.

The International Energy Agency said last month China needed to take more measures to encourage efficient use of electricity, highlighting the waste of power and environmental pollution from mostly coal-fired power plants.

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