Shanghai faces power restrictions again this winter.
Some businesses will have to shift production to non-peak times or reduce use of electricity at short notice.
Plans to control power use have been finished and will apply from December 15 to March 4, the Shanghai Electric Power Co said yesterday.
But officials said restrictions will only be imposed as demand and supply require.
"The shortage is smaller than in summer and a warm winter could help to reduce the demand," said Chen Ming, a senior engineer with the company's dispatching center.
Meteorologists have predicted a warm winter because of the El Nino phenomenon.
If the winter is mild, fewer residents will crank up their heaters.
Officials also believe central government measures to cool the economy will help reduce demand.
Power restrictions affected more than 5,000 businesses last summer, but officials said the number would be much smaller in winter.
In Changning District, more than 60 companies have been placed on the district's list to stop production in peak times.