Average monthly household electricity bills could increase by around Y1,000, or 18%, in fiscal 2012 if nuclear power plants are not restarted after regular inspection and thermal power generation is boosted to make up the shortfall, the Nikkei reported in its Monday evening edition.

Inspection schedules mean that all the nation's 19 operating reactors could be shut down by spring 2012.

Based on April prices of fuels such as coal and liquefied natural gas, using thermal plants to fill the role of nuclear reactors could increase fuel costs in fiscal 2012 by Y3.47 trillion, according to the estimate by the Institute of Energy Economics , Japan --a Ministry of Economy, Trade and Industry-affiliated body.

If these higher costs are passed onto power bills, electricity prices will increase by Y3.7 per kilowatt-hour. A typical household consuming 260-300kwh a month would face an average hike of Y1,049, or 18.2%.

The institute said the rise would also have a negative impact on the global competitiveness of Japanese manufacturers and other businesses. It also said that purchases of large volumes of fuel could affect the worldwide supply-demand balance, meaning Japanese utilities may have to pay more for fuel and raise bills more than estimated.

The institute also estimated that Japan 's carbon dioxide emissions in fiscal 2012 would be 18.7% higher than in 1990, and that average emissions in the five years through March 2013 would increase by 8.8%.

Under such a scenario, Japan would find it very difficult to meet its Kyoto Protocol pledge of reducing emissions by 6% from the 1990 level over a five-year period from 2008 through 2012.

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