WASHINGTON, D.C.: Every time your air conditioner or furnace rumbles on, greenhouses gases spew into the air. All those volts —about 10,900 kilowatt-hours per person — used to charge laptops and phones, light rooms, and keep the refrigerator running don’t come without an environmental cost. American electricity generation contributed 2.04 billion metric tons of carbon dioxide in 2014, clouding the earth’s atmosphere with emissions and worsening climate change….