Dishwashers

On the face of it, you'd think a machine that takes over an hour to do your dishes would be horrendously more energy-intensive and wasteful of resources than doing them by hand. (Not that you give a toss about that when faced with the choice of standing in the kitchen and tackling that mountain of crockery, or popping it all in a machine and going off to have a sit down.)

But in fact modern dishwashers use only about as much water as you would to fill the sink. And it really doesn't take much power to make the spinny thing with the nozzles on go round. Yay for dishwashers!!