How to choose a power strip

Question: How do you choose a good power strip for power surge protection? Are all power strips alike? Plus, this may seem like an idiot question but when the switch on the power strip is in the off position, is there still surge protection? –Del

Answer: Let me go over the various power issues and the options you have to protect your equipment. That should answer your questions.

Power from your wall socket is not always perfect. Fluctuations in the power supply can play havoc with sensitive computer equipment, resulting in data loss. In some cases, repeated power fluctuations or one a nasty power spike can fry your components.

Power irregularities can include the following types of conditions:

  • Brownouts — Short-term voltage decreases. This is the most common power problem, accounting for 87% of all power disturbances according to a study by Bell Labs. They are typically caused by the start-up power demands of many electrical devices. To make matters worse, brief small brownouts (also sometimes called “sags”) can occur without your even being aware of them, but over time their damage can mount up.
  • Blackouts — Total power losses, resulting from a loss of power from your utility, or any major interruption between your house and the pole your main electric line comes from.
  • Spikes and impulses — Dramatic voltage increases, similar to the force of a tidal wave. A spike can enter electronic equipment through network, serial, or phone lines, and damage or completely ruin components.
  • Surges — Minor short-term voltage increases. High-powered electrical motors, such as those on air conditioners and household appliances, cause this. When the equipment is switched off, the extra voltage is dissipated through the power line.
  • There’s also a potential for “noise“, which is electromagnetic and radio frequency interference.

Is it alright to simply plug a computer into a wall socket? Some people like to think so. Of course, with the proliferation of devices on, under, and around most computer desks these days, this is often not an option, since there may not be enough wall sockets. Even if a plug is available, however, plugging straight into the wall leaves your equipment dangerously susceptible to power fluctuations, and is therefore not recommended.

The next option is to use a power strip. This device plugs into one outlet and the various computer devices plug into it. Basically, it is a power outlet extender.

Some power strips come with surge protection, which protects your equipment from surges and spikes. (If your power strip has surge protection, then yes, even when it is switched off, it still is protecting whatever is plugged into it. And that was not an idiot question!)

The safest option is an Uninterruptible Power Supply, usually called simply a “UPS” (some people call them “power conditioners”). A UPS is a device that protects the systems from power irregularities mentioned above. Some UPSs have a built-in battery that will keep your computer running for a little while when the power goes out. The idea behind that is to give you enough time to shut down the system properly and safely, without losing any data or work.

Generally, there are two types of UPS — offline and online. An online UPS provides constant power from its own inverter so that, in the event of a power problem, there is no time delay between the power failing and the battery kicking in. An offline UPS monitors the power line and switches to battery power as soon as it detects a problem. That switchover takes a few milliseconds, during which the computer receives no power.

An off-line UPS is also sometimes known as a line-interactive UPS or a “standby” UPS. These are ideal for the home and small businesses. An online UPS can cost much more than a standby UPS, and would normally be used for mission-critical systems such as a server or a business computer. A standby UPS only protects against surges, spikes, and blackouts. A line-interactive UPS protects against the previous three items as well as under- and over-voltages. These use automatic voltage regulation and ensure that the incoming power is regulated at 110 to 120 volts.

Many people only connect the computer itself and monitor to the UPS, but you might want to connect peripheral items like modems or inkjet printers. (Laser printers should not be plugged into a UPS with your other devices because they have enormous power demands and need their own UPS system. The price of a heavy duty UPS system that can protect a laser printer is often more than the replacement cost of the printer.)

James Little at Belkin Components suggests using the following technique to determine the right UPS for your needs: Decide which pieces of equipment need UPS support. Next, figure out the wattage ratings for each piece of equipment you want to protect. There’s a sticker somewhere on most equipment (often on the back or the bottom, usually near the power source) that has this information. Manufacturers vary in how they express power draw so you may have to convert numbers to determine “VA” load. A little math is required here, so go get your calculator.

  • If the power draw is expressed in amps, multiply that by your nominal line voltage (which in North America is 120 or in Europe is 220). My computer shows ” 4.0 A”. So I’d multiple 4 x 120 to get a 480 VA load.
  • If the power draw is expressed in watts, multiply the nominal line voltage by 1.4 for VA load. You might want to check with your local computer store or tech support line for help with these ratings.

Do the same for the monitor and all other pieces of equipment you plan to plug into the UPS, and add the VA load numbers together. Once you have calculated the total VA draw of you equipment, select a UPS that is rated equal to or higher than the number generated. It’s important not to overload a UPS system, because excessive loads will trip its circuit breaker. Remember, it’s there to protect your equipment and it doesn’t know or care whether an overload was caused by a human or the power itself.

Although frequently overlooked, power spikes can come into your systems through your phone, cable, or other network connections, just as they can through the wall socket, so it’s a good idea to pick a UPS that has places to plug in those connections as well.

Belkin, which sells a variety of quality UPS products, has an UPS wizard on its Web site that will help you find the correct UPS. You can access it at
If it asks your location, be sure to select the US region closest to you, because there are no Canadian provinces listed, though Little promised to fix this.

APC is another maker of quality UPS systems. They have a wizard at

If you’re looking for UPS power solutions on-line, has a good selection. Or check out the variety on

In Canada, FutureShop and CompuSmart carry UPS systems.