A Switched-Off PC Is Still at Risk in a Blackout, Engadget Warns

According to the report, a powered-off machine stays connected to a home's electrical wiring, and that connection is the route by which damage occurs. Motherboards, RAM and solid-state drives are built with delicate circuits that are sensitive to unexpected voltage spikes.

The danger is not confined to the moment service is lost. Voltage can fluctuate sharply in the moments before and after an outage, Engadget said, and the surge that arrives when power is restored is often more damaging than the outage itself. Standard household circuits in the United States operate at 120 volts, and even moderate spikes above that level are enough to permanently damage sensitive components.

Turning a PC off before the outage does not remove the risk. Electricity can still travel through the cord and reach internal parts once power comes back on, even while the machine is dark, the report said. Surges most commonly occur when there is a sudden jump in current, often triggered by lightning or damage to nearby power lines. A strike that does not directly hit a house can still send a surge through a local transformer and into the home's wiring, and the grid typically delivers an additional spike when it comes back online.

A sudden loss of power while a computer is running brings separate problems, according to Engadget. Files being saved or updated may be corrupted, and an interruption during an operating system update could leave the system unusable. Machines equipped with mechanical hard drives can also suffer damage to their heads.

The report recommends shutting down and unplugging a system from the wall when extreme weather is forecast, and it says a machine should still be unplugged if the power has already gone out. Routers, described as among the most frequently fried devices in an electrical storm, should be treated the same way, along with televisions and other expensive electronics. On a desktop PC, switching off the power supply unit can help by preventing current from entering the system, though the report cautions that an extreme event such as a lightning strike could still cause damage.

A surge protector is described as a better defense, absorbing voltage spikes before they reach equipment. An uninterruptible power supply goes further by combining surge protection with a battery backup; it is not intended to keep devices running for hours, but it will carry them through short outages and give the user a window to save work and shut down in an orderly way. For wider coverage, the report suggests having a licensed electrician install surge protection directly in the electrical panel, which would shield every outlet in a house.

When power does return, Engadget advises against reconnecting everything immediately. It recommends waiting a few minutes to make sure the supply will not drop again, then plugging in the surge protector first, followed by the PC and any peripherals. The outlet notes that unplugging a computer takes only a few seconds and, combined with a surge protector or a UPS, reduces the chance of hardware damage or data loss.