My mother and I sometimes argue about what to do with the computer.
She says, “every time you get off the computer you have to take it off.”
I think the other way around, every two hours, someone spends half an hour on our computer.
So I think starting and shutting down every two hours uses more than leaving it on for a whole day.
Now I would like to know the correct answer from you.
thanks in advance
Answer
The energy consumption of computers depends very much on the hardware they contain, and without knowing this, this question is quite difficult to answer. I am therefore going to try to sketch a realistic situation, I hope it corresponds to yours.
The power (and therefore power consumption) of a powerful desktop computer when not in use (idle) is about 100W, but under load it is 500W. Let’s assume the first: the power consumption of a computer under load is then about 5 times more than when idle. The real numbers depend entirely on the components it contains, but I think that factor 5 is a good estimate even in a less powerful computer.
When starting up and shutting down, your computer is usually under high load for a short time. If it takes 1 minute to start up, you will use the same amount of power as if you later left that computer on for 5 minutes without doing anything. Result: 1 minute startup and 1 minute shutdown corresponds to (1+1)x5 = 10 minutes idle. So as soon as you are away from your computer for more than 10 minutes, shutting down and restarting later is the better choice.
Please note: this applies to leaving desktop computers standing up. Recent desktops and all laptops do have a sleep mode. In that sleep mode, they usually consume less than 5W. That changes the picture completely, because even if we take the rather high 5W, there is still a factor of 100 difference. Turning it off and on again instead of using a sleep mode is then only beneficial after (I take some off to compensate for the higher consumption when going into and out of sleep mode) for about two hours.
Conclusion: leaving the computer running without further ado is only beneficial if you have to go to the toilet. If a computer is used several times a day with, say, an hour or two in between, use a sleep mode. If there are several hours between each use (because everyone is at school or work, or at night), turn it off.
What you should always turn off is the screen. It also consumes quite a lot of power in sleep mode (sometimes more than a computer in sleep mode), and hardly needs any time or extra energy to start up: here you are always advantageous with switching it off. The same goes for sound systems and other connected equipment or extras. Printers and scanners are sometimes not used for a week, and when they are used often only for ten minutes. It makes no sense to leave them switched on: only plug them in when you use them.
Answered by
drs. Joachim Ganseman
computer science, digital signal processing, with a focus on editing and processing audio and music data
Prinsstraat 13 2000 Antwerp
http://www.uantwerpen.be
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