Should I turn my computer off at night?

The issue isn't quite as clear as one might think. There are two issues at play here: power usage, and for lack of a better term, "stress" on individual pieces of hardware.

Power's actually the easier one.

In most cases Standby is "almost as good as" turning your computer off. Standby typically uses a little power to keep certain components ready to be used, but components that use a the majority of the power are actually turned off when the computer is placed on standby.

That being said, I almost never use standby - however my reasons have nothing to do with power saving or device wear and tear.

The only thing standby really does for you when it works it to save the state of your machine so that when you power on you don't have to go through the entire boot and application start sequence. Personally, that's only important to me if I'm using my laptop and want to preserve the battery life during the day without repeatedly rebooting.

In addition, I also seem to periodically experience problems with device drivers that don't resume from standby properly. This has definitely improved over time, but I still get bit occasionally. Particularly for overnight scenarios, if I'm going to turn the computer off, I'll actually turn it off and let it do a "real" reboot when I turn it on in the morning.

But if standby works reliably for you, then I'm happy to consider is "close enough" to a complete power off for purposes of power use.

One last item to throw in to, and perhaps further confuse, the power issue is that your computer may already be taking steps on its own to minimize power usage when you're not using it. "Energy Star" compliant monitors, for example, will effectively go into the equivalent of standby all on their own if you don't use your computer for some period of time. Some computers will automatically turn off hard drives after some period of inactivity as well. So it's quite possible that, depending on your computer, simply by walking away from it you'll reduce the amount of power it's using. It's not as great a reduction as explicitly selecting standby, or turning the computer off, of course, but it's a step.

Now, let's talk about hardware and stress.

There is an argument that says leaving a component on continuously is less stressful on the component than turning it on and off repeatedly. While saving power, that stress contributes to earlier failure and required replacement. The argument goes that the eventual cost of replacing a broken device is so high (in terms of both purchase price and environmental impact) that in the long run it would have been more cost effective to simply leave it on all the time.

The counter argument is that most components today are built with this in mind. Indeed, as I mentioned earlier many components will turn themselves "off" after some period of inactivity whether you tell them too or not. The devices are, themselves, built for, and choosing to, power cycle fairly frequently.

And in almost all cases, the devices are lasting longer than we need them. By that I mean in most cases devices are replaced not because they broke, but because newer and more powerful devices have been purchased.

As you can see, the answer is much less clear on whether, and how often, one can safely turn off the power to your computer.

One thing I will add that isn't technically part of this question, but impacts your computer's lifespan more than power cycling is ventilation. Make sure that your computer has good airflow through and around it, and make sure that dust doesn't accumulate on or in it. Excessive heat is more of a danger than the number of times you turn the computer off and on.

The bottom line.

Confused yet? It wouldn't surprise me. The problem is that there's no real clear answer.

My expectation is that a "normal" user who uses their computer perhaps for a few hours a day would most likely turn it off, or put it into standby, when it's not going to be used for a few hours or more. And that's simply to minimize power use. It's also not a big deal if they don't.

Personally, I make the decision based on how I use my computers. That means that all of my computers are on 24 hours a day. But as you might expect, I use several computers heavily for long periods of each day. And more importantly, over night they all execute critical back-up and synchronization tasks that I rely on.