We are constantly being bombarded with messages to turn devices off at the mains, rather than leaving them on standby. But is it worth it? How much energy does this actually save?
According to the Lawrence Berkeley National Laboratory a television left on standby uses about one-and-a-half watts. For comparison purposes, a power shower uses between 7500 and 10800 watts. That means that for one fewer ten-minute (9 kW) shower you can leave your TV on standby for another forty-one days and still have used less electricity than you would have.
A study published in 2010 in the Proceedings of the National Academy of Science showed that people were far more likely to select curtailment activities (turning things off) rather than efficiency savings (like cutting a minute off your shower), despite efficiency savings being more likely to reduce energy consumption. Turning devices off at the mains, rather than making choices that would save far more energy, is another example of this.
The other interesting general rule of thumb: if you can enclose it in your hands and it isn’t warm to the touch, it’s wasting less than 10p/ year of electricity (may have changed recently with electricity prices, it’s been a while since I ran the numbers).