By 2030, the network could produce 16% of electricity consumption in Europe, or about 563 TWh.

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Tepco generated about a third of that, 300.7 TWh, and sold 280.2 TWh, 28% of which came from its 17 nuclear reactors.

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We have indicated that about 57 TWh of carbon-free power are needed, of which rooftop photovoltaic panels will supply 11 TWh.

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In 2009, Japan generated 956.5 terawatt hours (TWh) of energy, 30% of it from natural gas and 29% of it from nuclear sources.

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Under the less rigorous scenario with higher infiltration, gross electric energy needed would rise to 60 TWh, and the net to about 49 TWh.

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New York City can get by on slightly more electric energy than it is using now, about 57 TWh gross and 46 TWh net of PV production on buildings.

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And in Germany, solar producers have set a new world record, pumping an astounding 14.7 TWh of electricity into the grid during the first six months of 2012 -- 4.5 percent of the country's total power production during that period.

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The Department of Energy and Climate Change's (DECC) Renewables Roadmap estimates that biomass could potentially provide between 68 teraWatt hours (TWh) and 100TWh of renewable heat and electricity by 2020, which is 26-42% of the total needed to meet the EU renewables target.

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