A proposed petrochemical plant in western Pennsylvania would use -- and generate -- a substantial amount of power.The Beaver County Times reports that Shell Chemicals' ethane cracker plant proposed for Potter and Center townships in Beaver County would likely require more than 100 megawatts of electricity to operate. That would power 100,000 homes at any given moment, FirstEnergy Corp. spokesman Doug Colafella said.    "That's pretty massive," he said. "It would be a huge industrial customer."    Shell would use natural gas-fired cogeneration on site to create steam and electricity for the plant. Officials have said any surplus electricity would be sold for use in the regional power grid.    The proposed plant would convert ethane from Marcellus Shale natural gas liquids into chemicals used to make plastics, tires and even antifreeze.    The state approved lucrative tax breaks in 2012 as it competed for the project with other states. The deal approved by lawmakers in 2012 includes a tax credit of a nickel per gallon of ethane used by a qualifying refinery owner such as Shell. The credit, backed by former Gov. Tom Corbett, could start in 2017 and top $1.7 billion -- or $66 million a year for 25 years.    In June, Shell paid $13.5 million for the former zinc smelting site, located about 25 miles northwest of Pittsburgh.    The state Department of Environmental Protection said in June it had approved the company's air quality plan and several water-related permits for the site.    "The receipt of the air permit is a critical milestone for the project," the company previously said.    The company hasn't confirmed that it will build the multibillion-dollar plant. Officials have not produced a timeline on when a decision may be reached.