Whether you should turn off your computer at night is a complicated question, since some computers can benefit from being turned off at night, while others should be left on. Many people choose to turn their computers off to save power, increase security, and reduce wear on the parts. Others choose to leave it on for overnight-running processes, data sharing, and network or security updates. Ultimately, whether or not you turn off your computer at night is an individual decision, and you'll have to balance the pros and cons. If you have an unnetworked home PC, you may find that turning it off and unplugging it provides the most benefits.
One common reason to turn off a computer at night is its use of power. Those that are turned off use less electricity than those that are turned on, even when in idle or sleep mode. Desktop PCs use a lot more energy than laptops, so turning them off can make a more noticeable impact on the price of your electric bill. Though sleep mode does significantly reduce the amount of electricity used, a device in this mode will still use about a third of the power it uses when it is on.
Turning the computer off at night offers a small, temporary increase in security. When a computer is completely off, it is not susceptible to attacks from the Internet or unauthorized electronic access. Shutting the device off can also protect it from being accessed by onsite intruders simply because accessing a computer that is not already powered on takes longer. If you do decide to turn your computer off at night, then it's important to make sure that any operating system and virus software updates are completed before doing so, since turning it off could disrupt the update and leave you vulnerable to attacks.
Potential Increased Performance
Some operating systems benefit from being shut down and rebooted. For these, turning off the device at night ensures that the system has a fresh start in the morning, which can help eliminate crashes and slowness during the day. Other systems don't benefit from being rebooted though, and the process of restarting the computer and programs used during the day can take up a lot of time.
Turning a computer off at night can also decrease wear on certain parts of the hardware, like the fan and monitor. Since these parts are generally on when the computer is on, long-term, continuous use can cause them to wear out. Though you can do things to help prevent wear, like turning off the monitor and making sure the computer doesn't get too hot, leaving it on for a long time will still likely cause them to wear out more quickly than if you didn't. A computer that is on also collects dust, so leaving it on at night means you will have to clean it more frequently.
Despite this, turning the machine on and off every day can put stress on other hardware, like the Central Processing Unit (CPU) and hard disk. When the computer is on, these parts tend to get hot and expand, and then cool off and contract once it's turned off. The stress of expanding and contracting every day can eventually damage the hardware.
When to Leave It On
In some cases, turning off the computer at night is not recommended. If it is part of a work network and the administrator makes updates at night, you could cause problems or delays if you turn it off. Computers that house data and hardware needed by others on a network should also stay on. For example, if you access a printer through one computer, you will not want to turn it off unless nobody else is using it. If your computer acts as a communication device, like an answering machine, telephone or fax machine, it should also stay powered on whenever calls might come in.
Some users may turn off the computer because they think it will protect it from power surges, but this is not actually the case. Even when turned off, the machine is still vulnerable as long as it is plugged in. Surge protectors, or unplugging the machine, can help prevent electrical damage.