evidence: The original passage from the essay (with the selective quote in italics) reads: "The concept of net energy must also be applied to renewable sources of energy, such as windmills and photovoltaics. A two-megawatt windmill contains 260 tonnes of steel requiring 170 tonnes of coking coal and 300 tonnes of iron ore, all mined, transported and produced by hydrocarbons. The question is: how long must a windmill generate energy before it creates more energy than it took to build it? At a good wind site, the energy payback day could be in three years or less; in a poor location, energy payback may be never. So Hughes said a wind turbine placed in poor conditions might not generate enough energy to pay back what it took to make the turbine, but in a good wind site it could pay back the energy in under three years. [...] Of course some energy is consumed in building a wind turbine and the pylon that supports it, Hanley says. But "the typical wind turbine will generate enough electricity to offset the energy consumed to create it in about 7.5 months or less".