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BOTTROP, GERMANY - AUGUST 21: Control system of a plus energy house on August 21, 2014, in Bottrop, Germany. An Energy-plus-house produces more energy from renewable energy sources, over the course of a year, than it imports from external sources. Photo by Ute Grabowsky/Photothek via Getty Images)***Local Caption***

BOTTROP, GERMANY - AUGUST 21: Control system of a plus energy house on August 21, 2014, in Bottrop, Germany. An Energy-plus-house produces more energy from renewable energy sources, over the course of a year, than it imports from external sources. Photo by Ute Grabowsky/Photothek via Getty Images)***Local Caption***