Your Computer - Leave it on or turn it off?

A frequent question that relates to the discussion of power supplies concerns whether to turn the computer off when it is not in use. Before making a decision to turn the computer off or leave it on, some facts must be understood about electrical components and what makes them fail. Because circumstances vary from computer to computer and environment to environment, the best answer is to combine this knowledge information with power consumption, cost and safety to the particular needs of the user.

Frequently, powering a computer on and off does cause deterioration and damage to components. This seems logical, and the reason is simple but not obvious to most. Many believe that flipping the computer power on and off frequently is harmful because it "shocks" the computer. The real issue, however, is temperature. It is not so much electrical shock as thermal shock that damages the computer. As the computer warms up, the components expand; and as it cools off, the components contract. This alone stresses everything. In addition, various materials in the computer have different thermal expansion contributors, which means that they expand and contract at different rates. Over time, this thermal shock causes deterioration in many areas of the computer.

Thermal expansion and contraction remains the single largest cause of component failure. Chip cases can split, allowing moisture to enter and contaminate them. Delicate internal wires and contacts can break, and circuit boards can develop stress cracks. Surface mounted components expand and contract at different rates from the circuit board they are mounted on which causes enormous stress at the solder joints. Solder joints can fail due to the metal hardening from the repeated stress causing cracks in the joint. Components that use heat sinks such as processors, transistors or voltage regulators can overheat and fail because the thermal cycling causes heat sink adhesives to deteriorate breaking the thermally conductive bond between the device and the heat sink. Thermal cycling also causes sockets and connections to "creep". This can cause a variety of intermittent contact failures.

Thermal expansion and contraction affect not only chips and circuit boards but also devices like hard drives. Most hard drives today have sophisticated thermal compensation routines that make adjustments in head position relative to the expanding and contracting platters. Most drives perform this thermal compensation routine once every five minutes for the first 30 minutes the drive is running and then every 30 minutes thereafter.

In essence, anything that can be done to keep the computer at a constant temperature prolongs the life of the computer. Although the best way to achieve this is to leave the computer on, this may not always be the best method. A computer powered on and left unattended can be a fire hazard, may be easily damaged if moved while running, and wastes electrical energy.

Based on these facts, computers should be turned on at the beginning of the work day and turned off at the end of the work day. Do not power the computers off for lunch, breaks or any other short duration of time. This is probably the best compromise to computer longevity taking all of these factors into consideration.