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Assuming I use it all day long, should I shutdown my (recent) laptop every night and power it up every morning, or just let it sleep by closing it?

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    If your goal is to be as energy efficient as possible, then it's best to turn it off (or hibernate if your OS supports that) AND unplugging it. If you keep a laptop plugged in it will try to recharge the battery every now and then. – THelper Aug 17 '17 at 8:27
  • But if you unplug it, it will still (slowly) discharge the battery @THelper? – Martin Tournoij Sep 3 '17 at 3:33
  • @Carpetsmoker good point! Yes, it will discharge slowly but for Li-Ion batteries (the most common battery for laptops) it will be very little and keeping a Li-Ion battery constantly at 100% will shorten its life. It may be beneficial to leave it plugged it over night every once in a while, but that depends on your charger. In any case, sleep mode will cost more energy than shut down or hibernate (plugged in or not). – THelper Sep 3 '17 at 11:40
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To determine the power used when the computer is in sleep mode you can acquire a power meter that plugs into a power outlet & measures the electricity used by devices that are connected to the power meter.

This has been done by one person who posted the results online. The summary states:

The standby mode power consumption is just a bit more than leaving the computer plugged in but off. So I can use standby mode without any significant additional cost.

While I'm away for more than 8 hours it makes sense to turn the computer off at the power strip. At this point no electricity is being used by any of the devices on the power strip. I usually do this when I am done using the computer in the evening or plan to be away for a while.

The reason why the computer uses power while it is in sleep mode is because all the computer processes are stored in RAM, which requires powers to maintain things in memory.

It comes down to you. Do you want to use electricity keeping the computer's memory active while you are not using the computer for long periods of time and then to have the computer be instantly available when you open it up again, or do you want to use no electricity and wait for the computer to boot up and go through its initialization procedures when you turn it on, after not using it for a long time.

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    The article is for a desktop computer but the OP asks about a laptop. The core difference being that as long as the laptop is plugged in, it might charge the battery when it sees fit. And that charging uses extra energy compared with e.g. the battery having been removed. So there's actually 4 states to consider: the combinations of standby/shut down with plugged in/unplugged. That doesn't really change much about your answer, but it could make a difference. Which should be measured to know how much it matters. – stijn Aug 16 '17 at 18:46
  • @stijn: Fair points, but what is also missing is the power consumed to restart the computer (and perhaps return it to the ‘steady state’): is that a significant element? Obviously it varies from one user to another, depending on how many programmes they keep running in steady state use of the computer. – PJTraill Aug 23 '17 at 13:07
  • @PJTraill I doubt that the couple of minutes (at max) it takes for starting up the computer is of any significance compared to all the hours it is powered on since the OP says the laptop is used all day long. But again: would have to be measured to make sure. – stijn Aug 23 '17 at 14:12
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    You need to be careful with power meters for these sort of low-power devices as not all of them measure low-power devices accurately. Many popular ones are only guaranteed to be accurate with 5W or more. – Martin Tournoij Sep 3 '17 at 3:32

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