Millions is off by an order of magnitude. In 2015 it was estimated that around 127k homes still used coal heating. Source, found on a ddg search: https://forg

Millions is off by an order of magnitude. In 2015 it was estimated that around 127k homes still used coal heating. Source, found on a ddg search: https://forgreenheat.blogspot.com/2017/06/trends-in-heating-with-coal-in-united.html https://forgreenheat.blogspot.com/2017/06/trends-in-heating-... Other sources give comparable numbers, in no case more than ~150k