This statistic from the BBC certainly woke me up this morning.
He has calculated that the CO2 emissions from electrical equipment being left on standby are equivalent to 1.4 million long-haul flights.
To put it another way, the entire population of Glasgow could fly to New York and back again and the resulting emissions would still be less than that from devices left in sleep mode.
Another number to illustrate the scale of the problem. Televisions alone produce nearly half a million tonnes of CO2 annually by being left on standby.