Surge Supressors

What is a surge, and why must we suppress it? I’m vastly oversimplifying, but electricity runs through the power lines and into the outlets in your home much like water in a hose. The water in a hose moves from an area of high pressure to an area of lower pressure. That’s why it flows down the hose. Voltage is like the measurement of the amount of pressure in the electric lines. Standard power in North America flows at 120 volts. A surge is like forcing too much water down the hose at once.

Things can occur that affect the voltage. The one that most people think of first is a lightning strike on or near a power line. That can cause a surge of millions of volts. No surge suppressor can withstand that kind of force. In the event of a lightning storm, your best bet is simply to unplug your computer from the power outlet.

There are other, more common things that lead to power surges. Big pieces of electrical equipment like elevators, air conditioners, and refrigerators can draw large amounts of power as they turn motors on and off. This causes the power level to surge. It can happen over and over throughout the course of the day.

The system of electrical distribution, from generators through power-lines and switch-boxes and transformers and eventually to the wall outlets in your home, is very complex, and there are many opportunities along the way for power surges to occur.

If the voltage increase lasts for three nanoseconds (billionths of a second) or more, it is called a surge. If it lasts less than three nanoseconds, it is called a spike. Spikes and surges can be very damaging to your computer equipment. In extreme cases, they can fry your power cord and even start a fire. Smaller surges can damage or destroy the delicate electronic components and microprocessors in your computer. If a surge doesn’t destroy the equipment outright, it can still significantly reduce the life-span of the computer.

So far, we’ve learned what a surge is and why we would prefer not to have it anywhere near our computers. That’s where surge suppressors come in. They are also commonly called surge protectors. A more official name is Transient Voltage Suppressor. I’m not going to get into a technical explanation of how they work. There are a variety of different methods used, but they all boil down to the same thing: suppress the extra voltage and keep it from harming your computer. Some suppressors divert the extra electricity to ground, some reduce it by absorbing it and letting it out at a more controlled rate. Some have fuses or circuit breakers built in that cut the connection altogether if the voltage gets too high. Most devices will use a combination of techniques.

There is a bewildering variety of surge protectors, with different features and prices, and levels of reliability and effectiveness. I’ll give you an overview of your choices, tell you what to look for in a surge suppressor, and finally, give you a step by step checklist to help you rate a particular model you’re considering.

Here are the main types of surge protectors:

  • Basic Power Strip – can be found for under ten dollars, has minimal or no protection from power surges.
  • Better Power Strip – same as the basic, but has slightly better ratings and perhaps a few more features. Can usually be purchased in the $15 – 30 price range.
  • Surge Station – Larger, more substantial units with serious protection and options to plug in phone and cable lines as well. These range in price from $30 to upwards of $150.
  • UPS – Uninterruptible Power Supply. These aren’t exactly surge protectors, but often do the same work as surge protectors. They also can smooth out the flow of electricity, eliminating tiny spikes and sags in the flow. These start around $150 and can go up into the thousands of dollars.

An Uninterruptible Power Supply has a built-in battery, and protects against three things:

  1. Surges & Spikes (just like a surge suppressor does)
  2. Voltage sags (brownouts, or when the voltage falls below the acceptable level)
  3. Power failures – the battery allows you time to shut down your computer properly without experiencing damage or data loss.

The UPS comes in two flavors – the Standby UPS senses when there has been a power fluctuation, and quickly switches over to the battery power. This doesn’t happen instantly, and for the small period of time before the switchover occurs, your computer is vulnerable. The other kind is called a Continuous UPS. The battery is constantly recharged from the wall, and your equipment is constantly fed a stable flow of electricity from the battery. This is the smoothest, most stable source of power, and is often preferred for servers or extremely important pieces of equipment. As you might guess, a Continuous UPS costs about twice as much as the Standby UPS.

A surge protector is like an insurance policy. You have to ask yourself what it is you’re insuring, and how important it is. Then you choose how much insurance you need, and how much you’re willing to spend for it. There is no one answer, but if you understand the question, you’ve got a better shot at answering it correctly.

What should you look for when purchasing a surge suppressor?

PRICE: Expensive doesn’t necessarily equal good, but cheap does mean bad. If you buy a $1.99 power strip, you will get what you pay for.

UL Listing: The Underwriters Laboratories is a non-profit organization that rates electronic devices. A UL listing doesn’t guarantee quality, but if the surge suppressor doesn’t have one, you’re probably looking at a piece of junk.

Indicator Light: The parts in a surge suppressor can burn out or stop working and there’s no way to tell. With an indicator light, as long as it is lit, you know that the device is in good working order.

RATINGS: Good models will have specifications listed on the package. Understanding these is the key to picking a good surge suppressor. The types of ratings are: 1) clamping: how may volts does the device let through before kicking in? 2) energy absorption/dissipation: how much energy can the device absorb or dissipate before failing? And 3) response time: how quickly does it go to work when a surge occurs?


  1. What are you protecting? How important is it? (For our purposes, we’re going to say “Computer” and “VERY!” – stereo and electronic equipment are also good candidates for protection)
  2. SUPPRESSED VOLTAGE RATING (Lower is better). This is the “clamping” we talked about above. How much energy does the device let through before it kicks in? 500 volts is ok, 400 volts is better, 330 volts is better still.
  3. STAGES OF SUPPRESSION (more is better, the number will be 1, 2 or 3)
  4. SURGE CURRENT RATING (this is how much electricity the device can handle, rated in amps; higher is better)
  5. ENERGY ABSORPTION/DISSIPATION (measured in JOULES – higher is better. 200 is minimal, 600 is good.) CLAMPING RESPONSE TIME: Faster is better. Measured in nanoseconds (billionths of a second) – 1 nanosecond or less is good – or picoseconds (trillionths of a second). Picoseconds are better than nanoseconds.
  6. INCOMING LINES PROTECTED – More is better. The number will be 1, 2 or 3.
  7. Warranty: Generally, the longer it is, the better. Good features to look for are a lifetime guarantee or an equipment replacement guarantee.