The PAC aims at using design to increase people’s awareness of their energy spending. The design is a flow in the power cord, which lights up whenever energy flows through it. We’d all like to be more energy-efficient. But watching the meter doesn’t intuitively show how much juice is being used minute to minute. The idea behind The PAC is different: what if you could actually see the electricity flowing into your machines? The more current, the faster the light spirals. In testing the device, researchers found that making the invisible visible, tuned consumers into their bad habits, nudging them to power down.