A Traffic Light That Tells Me When To Do Laundry

Electricity is not equally cheap or clean at every hour, but nobody in the house wants to read a graph before starting the washing machine.

So I built a small box with red, yellow and green lights. Green means now is a good time, red means wait. That is the entire user interface.

It sits where you see it in passing, and it turned an abstract number into something the whole family reacts to without thinking about it.