A power conditioner is an electrical device that provides "clean" AC power to sensitive electrical equipment. A typical power conditioner for home or office has up to 10 or more receptacles or outlets and commonly provides surge protection as well as noise filtering. Many models also provide Ethernet, cable and phone line conditioning.

Most people are familiar with surge protectors, which guard against damage due to sudden spikes in the electrical current. While surge protectors safeguard equipment, a power conditioner cleans the signal, eliminating interference on the line. This can translate to faster, more reliable network operations, improved modem throughput, better quality cable TV feed and superior audio/video for home theater systems.

Line noise can result from a number of issues including random fluctuations in the AC current, inferior or damaged wiring, interference from other machines or appliances, overhead fluorescent lighting or even bad weather. "Dirty power" impedes signal clarity by causing disruption of signal integrity. In the example of a television set, static translates to a visually degraded picture or "snow." Audio signals suffer distortion. A dial-up modem might get frequent disconnects, while static on a DSL or cable modem will negatively impact data transfer speeds.

A good quality power conditioner is designed with internal filter banks to isolate the individual power outlets or receptacles on the power conditioner. This eliminates interference or "cross-talk" between components. If the application will be a home theater system, the noise suppression rating listed in the technical specifications of the power conditioner will be very important. This rating is expressed in decibels (db).

The higher the db rating, the better the noise suppression. Good units start at a rating of about 40-60db for noise filtering. If a device does not state the db rating in its specs it may be better to move on to a different model or manufacturer.

For surge suppression, be sure the unit has an adequate "maximum watt" capacity for your needs. Plasma HDTVs, for example, use more electricity than LCDs. One popular 50-inch plasma HDTV is rated at 555 watts. With a multi-channel receiver and other components, wattage can add up in a home theater system.

The power conditioner will also have a "joule" rating. A joule is a measurement of power or heat required to sustain one watt for one second, known as a watt-second. Since electrical surges are momentary spikes, the joule rating indicates how much watt-energy the suppressor can absorb at once before becoming damaged itself. The higher the joule rating, the greater the protection.

Today's computer and home theater systems represent substantial investments. For this reason some high grade power conditioners come with monetary guarantees against damage to connected equipment due to electrical surge -- in some cases up to US$500,000. These particular power conditioners also come with lifetime guarantees. Considering their cost, they are a worthwhile investment to protect equipment and provide clean power for the best possible audio/visual experience.

A fine grade power conditioner with all of the features mentioned above and a noise suppression rating of 60db might have a list price of well over one hundred US dollars, but can usually be found for US$69-$99 with some diligent shopping. Units with list prices in the two-hundred dollar range normally have extended LED indicator lights and are "flashier." They might also have higher wattage and db ratings, but this is not necessarily true, so check specifications.

Although the term "power conditioner" is often used interchangeably with "line conditioner," these terms can also refer to devices that not only condition power but also regulate voltage. This type of line conditioner, often used in industry, will boost voltage when it drops or act as a surge protector when it peaks, maintaining a steady flow of electricity within a set range of voltage parameters. The typical power conditioner used by the householder for computer and home theater systems does not commonly include voltage regulation.