Shanghai doesn't have big oil fields or coal mines, but it has 200 million square meters of roofs.

　　Energy specialist Cui Rongqiang says all those roofs provide the perfect substitute for traditional energy sources.

　　According to Cui who is director of the Institute of Solar Energy at Shanghai Jiao Tong University, every roof can be transformed into a small solar generating unit. Given the city's average annual amount of sunlight, even 100,000 roofs could generate 430 million kilowatt hours of electricity every year.

　　Sunlight should not be wasted, Cui says.

　　True, especially when improving efficiency through new technologies is perhaps the only feasible way to ensure sustainable development in the country.

　　This is easy to understand if we consider the underlying reasons for China's resource-intensive growth model.

　　Industry produces 53 percent of China's total gross domestic product, while the service sector accounts for only 34 percent. Typically, energy consumption per unit of GDP in the industrial sector is 4 to 5 times more than the service sector.

　　In developed countries and many other developing countries, the service sector is much more advanced than here.

　　More disturbing, China's industry is dominated by heavy industry. It mainly exports low-end, resource-intensive products and imports high-tech equipment. The energy used for producing one US dollar of steel is much higher than the equivalent for microchips.

　　Wu Jinglian, a renowned economist with the Development Research Center under the State Council, has repeatedly said China should leap over the heavy industry phase in its modernization drive.

　　Many scholars, including Zhao Jianping, a senior energy specialist with the World Bank, are skeptical of this view. According to Zhao, Wu's suggestion may help relieve the energy problem, but it doesn't look like China is going to leave the steel and chemical sectors behind any time soon.

　　"China is not ready to step out of heavy industry yet. It takes time," Zhao says.

　　In fact, Zhao says heavy industry's share in the overall industry sector has increased in the past few years.

　　The high proportion of coal- 67 percent - in total energy consumption is another crucial factor that contributes to the energy problem. Coal combustion is much less efficient than natural gas and oil combustion. Internationally, coal only accounts for 26 percent of world energy consumption. But due to China's limited resources, the coal proportion of energy consumption will not drop below 60 percent until at least 2020.

　　A quick structural change - either in the overall economy, the industrial sector, or energy consumption - to secure a sustainable growth model, is unlikely to happen in the short-term.

　　Fortunately, there are huge gains to tap by increasing energy efficiency.

　　Energy consumed per unit GDP in China is well above the world average. In case of oil consumption, it is generally thought China uses three times more oil to produce one unit of GDP than the world average and seven times more than Japan.

　　According to Zhao, China's energy consumption in most standard industrial processes, transportation and home appliances is 20 to 100 percent higher than developed countries.

　　In similar climates, heating residential buildings is estimated to consume 50 to 100 percent more energy, compared with Western Europe and North America, Zhao said.

　　An astronomical amount of energy can be saved with technical innovation. Energy efficiency is crucial to the future of the country.

　　The investment required may be high initially, but it will pay off eventually.

　　Take solar power generation on roofs for example. The investment is about 150,000 yuan (US$18,495) for one solar roof. It looks daunting at first, but one power generation set can be used for 30 to 35 years. Plus the maintenance cost is minimal. Then there's the environmental benefit as well.

　　Shanghai could pilot the project and convince other cities across the nation of its benefits.