How much energy does a computer use on standby?

A laptop usually uses two watts of energy when it is on sleep mode, while a desktop computer uses around five to 10 watts. The energy consumption of computers while on standby is significantly lower than their consumption if they were running in normal mode all the time.

Due to the insignificant difference in energy consumption when you put a computer on sleep mode versus when you shut it down then turn it on again, the U.S. Environmental Protection Agency (EPA) actually recommends just using sleep mode whenever the computer is idle. According to the EPA, setting your computer to go into sleep mode when it is not being used is a very efficient way to reduce your energy consumption.