What causes surges?

The primary source of surges and spikes in most homes is appliances. When a large, motor-driven appliance shuts off (either manually, automatically, or due to AC power failure), energy stored in the motor coils can flow back down the power line, a phenomenon called inductive kick. It typically shows up as a spike of about 500 volts that lasts somewhere between a few microseconds and a couple of milliseconds. Inductive kick can come from appliances such as refrigerators and air conditioners, or from industrial devices such as elevators and machine tools.

The primary source of surges and spikes in most homes is appliances.
The other most common source of spikes and surges is lightning, but most lightning surges aren’t caused by direct strikes. They’re caused by lightning passing near your local power lines. The magnetic field produced by the lightning generates high-voltage electricity in the lines, which can flow into your home. If your home or power line suffers a direct lightning strike, it’s unlikely any consumer surge protector can absorb the millions of volts involved.
The obvious conclusion here is that some people need surge protection more than others. If you live where lightning storms are common, good surge protection is a must. If you live where lightning storms rarely occur, it’s not as big a concern. Likewise if you have a lot of large appliances, or you work in an office that’s part of an industrial facility, surge protection is more important.

Also, note that many electronic devices have their own MOVs built in, and many aren’t all that vulnerable to minor surges in the first place.


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