If it were built (at an estimated cost of $400 million), 10MW could pay off its energy debt in 20 years. Extra juice feeds the municipal grid, and other sources in the area would adjust for the tower's output. The building could house offices or residences or both, says designer Robert Ferry, 35, who helms the Dubai architecture firm Studied Impact with his wife, Elizabeth Monoian. The pair became interested in energy-generating skyscrapers on moving to the United Arab Emirates, where there are superstructures in spades but few that are any greener than their brochures. With the 10MW Tower, they hope to someday create a power plant you can live in. It may sound fantastic, but, Ferry says, "it's only a matter of time before something like this is built."