Just guessing, but if there are two households where there was one, you have two furnaces instead of one, two refrigerators, more air conditioners, more lawns to water . . . you get the idea. Things that once were shared that now have to be duplicated.
And the same applies to single adults in general. In short, 95 percent of the environmentalist movement, being never-married or divorced, is the biggest group of resource hogs on the planet.
ahhhhh....got it. thanks!