Although all commercial device-level surge suppressors connect in the same way–you plug the surge suppressor into a wall outlet, then plug your computer or peripherals into the surge suppressor–the active components inside the suppressor may actually be connected in parallel or series with your computer.
A series-connected surge suppressor acts as a roadblock. The surge must travel through the suppressor on its way to your computer. The suppressor removes or smoothes out the surge on its way so, in theory, no dangerous voltages are left to harm your equipment.
A parallel-connected surge suppressor is connected in parallel to your computer, across the leads of the power line just as is your computer. The suppressor works by shorting out (or shunting) the surge, routing its high voltage directly from hot to neutral, before the surge voltage on the power line rises to a point at which is can damage your computer.
Engineers design parallel-connected surge suppressors so they only conduct electricity (and thus generate that short circuit) only for the duration of the overvoltage of the surge. As soon as voltage falls back to normal, the surge suppressor removes the short circuit, at least if all goes well. Most surge protectors are parallel, and most engineers would recommend the parallel design.
A series-connected surge protector must be located between the source of the surge and your computer. A parallel-connected surge protector could, in theory, be located anywhere in an electrical circuit as long as it can provide a substantially lower resistance path to ground than does the circuit of your computer’s power supply. As a practical matter, however, even series-connected surge suppressors are interposed between utility power–the surge source–and your computer.
The most common surge suppressors take the form of outlet strips. These function at the device level or, as described in the industry, at the point-of-use. They are meant to protect only a single device or a few devices, the equipment that you plug into them.
A chief characteristic of these point-of-use surge suppressors is that they are inexpensive. They are also relatively convenient. Not only can you buy a point-of-use surge suppressor for a few dollars–you can likely find inexpensive (and, perhaps ineffective) surge suppressors in the discount store for $5, although better products may cost $50 to $75, or even $100–but also they require no installation other than to be plugged in.
The alternative is whole-premises or whole-house surge protection that is installed in your fuse box or breaker panel. Whole-premises surge suppressors have the advantage that they protect everything in your home or office against external surges. Surges get stopped before they get into your house.
But whole-premises surge suppressors are not as effective at protecting against surges that arise inside your home or office, such as those from appliances–for example, the surges that pop up when a refrigerator compressor starts or stops. On the other hand, internally generated surges are unlikely to harm your equipment the way a good lightning strike will.
The disadvantages of whole-premises surge protection are cost, and the need for an electrician to install the protection device, because it must be connected directly to your fuse box or breaker panel. Premise protection starts at about $75 for the unit, and will probably cost up to $250 installed (note that we’re somewhat leery of units that low in cost, with higher-end brands starting around $200). You can also find companies offering monthly contracts for around $5/mth or so. Due to the installation inconvenience, most people opt for point-of-user surge suppression.
Nothing prevents you from using both whole-premises and point-of-use surge suppression together. In fact, many experts recommend using both to gain the utmost in protection.