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Power Conditioner Buying Guide

Power Line Conditioning for Computers, Electronics & Audio/Video Equipment

This buying guide will help you:

  • Understand what a power conditioner is and recognize key features
  • Learn the questions to ask when purchasing a power conditioner
  • Find answers to frequently asked questions about power conditioners
power conditioners and line conditioners

Power Conditioner Basics

What is a Power Line Conditioner?

Also known as a voltage regulator, a power conditioner protects sensitive electronics, such as computers, lab equipment, home theaters from voltage fluctuations and power surges. It also removes electromagnetic and radio interference from the AC line so amplifiers, radios and other audio/video equipment perform at their best.

Why do I need a Power Conditioner?

Nominal voltage is the name given to a range of voltages. In North America, nominal voltage is 120V, but for a variety of reasons, you will rarely get exactly 120V from the outlets in your home or office. Power companies try to maintain actual voltage within ±5% of the nominal voltage (114–126V in North America, 228-252V elsewhere) but more significant over- and under-voltages can occur.

example of north american voltage ranges

Fig. 1: Example of North American Voltage Ranges

When the power supply to a device falls out of the service voltage range, the device may shut down, malfunction, or suffer damage to its circuit board. Poor power quality over an extended period may cause premature failure of the device. Power conditioners with Automatic Voltage Regulation will trim or boost voltage to maintain the service voltage range.

What causes voltage fluctuation?

These are some of the more common causes of voltage fluctuation.

Changes in demand for electricity in the power company's system due to factors such as weather or time of day

The distance of an outlet from the meter or from the meter to the power company's transformer (power pole)

Proximity to a factory or other large consumer of electricity

Starting or stopping common household appliances, such as a refrigerator or vacuum cleaner, especially on an already overloaded circuit

What benefits can I expect from a Power Conditioner?

  • Protect sensitive electronic equipment from damage or data loss
  • Improve the quality of audio recording or playback by removing line noise that causes "hum"
  • Extend the life of equipment containing electronic circuits

Key Features

Automatic Voltage Regulation (AVR) – Stabilizes incoming AC power by boosting low voltages and trimming high voltages so connected devices get the voltage they were designed to use (nominal 120V or 220-240V, depending on your country). Voltage regulation is sometimes called "buck and boost".

"Let-Through" Rating – The let-through voltage rating refers to the average amount of voltage the power conditioner "lets through" to connected equipment following a surge or spike. The lower the let-through rating, the better the surge protection. The UL 1449 rating levels are 330, 400, 500 and 600 volts.

Joule Rating – A power conditioner's joule rating indicates how large a power surge it can absorb without failing. You should choose a joule rating based on the value, importance and sensitivity of the equipment that will be connected to the power conditioner. For more sensitive or costly equipment, such as computers, televisions, lab equipment and audio/video equipment, select a power conditioner with a rating of at least 1,000 joules.

Line Noise Filtering – Line noise is the result of electromagnetic interference (EMI) and/or radio frequency interference (RFI) and is typically caused by other equipment operating on the same electrical circuit (e.g. fluorescent lights or a vacuum cleaner). You may experience line noise as a buzz or hum from your speakers or radio transceiver, or "snow" on a television picture. Line noise filtering removes noise from the incoming AC power and is expressed in decibels (dB), with a higher dB rating indicating better noise suppression.

How to Choose a Power Conditioner

These five questions will help narrow down your choices.

1 How much power does your equipment need?

To estimate power capacity requirements, add up the wattage of the devices you plan to connect to the power conditioner. Refer to the nameplate or manufacturer's documentation for each device to find its wattage. If output is listed in amps, multiply by the nominal AC voltage to estimate wattage (e.g. 3 Amps x 120 Volts = 360 Watts).

2 What voltage does your equipment use?

The AC input voltage of the power conditioner should match the voltage of the equipment connected to it. For homes and offices in North America, the voltage is typically 120V and the input plug type is NEMA 5-15P, which is the familiar grounded power plug used in most households. In Europe and elsewhere, nominal voltage is typically 230V and the plug type will vary from country to country.

3 What type and number of outlets do you need?

Count the number of devices that you plan to plug into the power conditioner and choose one with at least that many outlets. Also pay attention to the input and output plug types. The power conditioner's input plug and outlets should match the plugs on the equipment you'll be connecting.

line conditioner 120v 5-15p
Plug Type: NEMA 5-15P
Voltage: 120V
Rated: 15A
line conditioner 20a 5-20p
Plug Type: NEMA 5-20P
Voltage: 120V
Rated: 20A
line conditioner 230v 6-15p
Plug Type: NEMA 6-15P
Voltage: 230V
Rated: 15A
line conditioner 20a c19
Plug Type: IEC-320-C19
Voltage: 230V
Rated: 20A

4 Which form factor works best?

Tower - A tower power conditioner is shorter in width than height (or roughly the same) and typically has outlets in back. It can be placed on the floor behind the equipment it is protecting, or on a desk or shelf.

Rack Mount - A rack-mount power conditioner is specially designed to be mounted inside a standard 19-inch rack enclosure or open frame rack (almost all racks use the 19-inch standard). The power conditioner's rack height tells you how many vertical rack spaces it will require. One rack unit (abbreviated to 1U) is 1.75 inches (44.45 mm) high. Outlets are typically on the back of a rack-mounted power conditioner.

Wall Mount - Some power conditioners come with mounting "ears" so they can be securely attached to a wall or bench, saving floor-space and preventing accidental disconnections.

5 How valuable is the equipment attached to the power conditioner?

The value of the equipment you want to protect is the most important consideration when choosing a power conditioner. Devices that are critical to work/home life and those that are otherwise costly or fragile require a greater degree of protection.

A power conditioner's job is to regulate voltage and to absorb the brunt of power surges and spikes so your equipment doesn't have to. This will take a toll over time. In addition to AVR and good Joule rating, look for models that come with insurance to repair or replace any connected equipment damaged by power surges (USA, Canada and Puerto Rico only).

Other Features to Consider

C14 Outlets - C14 to C13 power cables are a popular way of connecting a server or switch to a power source in a server room or network closet. A power conditioner with a mix of NEMA 5-15R and C14 receptacles provides options for connecting and placement of devices.

LEDs for Power Monitoring - Real-time diagnostic LEDs indicate if your incoming voltage is being boosted or trimmed. They can also detect common wiring faults in wall outlets, such as loose wiring or improper grounding.

Input Breaker - A resettable breaker protects the electrical circuit from excessive current draw. If the breaker trips, you can remove some of the equipment plugged into the power conditioner and reset the breaker.

Physical Size - Most tower line conditioners are small, but extra-small models are available for especially tight spaces, such as a shelf or behind a piece of equipment.

Power Conditioner Comparison Chart

Form Factor Tower Small Tower Wall-Mount Rack-Mount
Input Voltage 120V or 230V 120V or 230V 120V 120V
Output Wattage Up to 2,400W 600W 600W 2,400W
AVR Range 85-147V
87–140V 89-147V
Surge Suppression 1220-1440 joules 340-720 joules 720 joules 1440 joules
Noise Filtering Up to 80 dB 20 dB 20 dB 80 dB
Outlets Up to 6 Up to 6 4 14
  Explore Explore Explore Explore

Alternative Power Quality Solutions

Isolation Transformers

An isolation transformer transfers electricity from a primary circuit such as the AC power supplied by an outlet, to a secondary circuit such as a medical device or lab instrument, without a physical connection between the circuits. The electrical isolation protects against electric shock and suppresses electrical noise that can interfere with sound quality.


power conditioner vs isolation transformer

Surge Protectors

The main job of a surge protector is to protect connected equipment from power surges above the surge protector's "let through" voltage. Some surge protectors also filter out line noise from incoming AC power supply.


power conditioner vs surge protector

UPS Systems

A UPS with AVR does everything a surge protector or line conditioner can do, plus it includes a battery that allows equipment to remain powered through short-duration power failures. Like power conditioners, many UPS systems have voltage regulators that keep voltage in an acceptable range.


power conditioner vs ups system

Product Features Compared

  Surge Protectors UPS Systems with AVR Power Conditioners Isolation Transformers
Protection Against Surges and Spikes
Protection Against Brownouts
EMI/RFI Line Noise Filtering
Voltage Regulation
Battery Backup Power
Electrical Isolation
Typical Street Prices (USD) $40 $150 $200 $350
  Explore Explore Explore Explore

Nominal voltage varies by country and application.

Average reseller price. Actual prices vary.

Questions & Answers

What is an acceptable voltage range for a 120V circuit?
In the United States, National Electric Code article 210-19 FPN No. 4. suggests a 5% maximum combined voltage drop on the feeder and branch circuits to the furthest outlet "will provide reasonable efficiency of operation." The Canadian electrical code also requires no more than a 5% drop between the meter and outlet. Applying the 5% tolerance gives a nominal 120V range of 114V to 126V.

Can I use a power conditioner with my generator?
Yes, a power conditioner will stabilize the voltage from a generator. However, it will not convert the modified sine wave produced by some generators to pure sine wave, making those generators unsuitable for sensitive electronics.

How to Choose the Best Power Conditioner for a Guitar Amp

Should I use a power conditioner with my laser printer or copier?
Yes, but not with the printer itself. Printers and copiers use a hot roller called a fuser unit to bind ink toner to the paper as it passes through the printer. Periodically, the printer needs to reheat the fuser unit to the required temperature, and this requires a lot of electricity. To prevent a power sag (under-voltage) from impacting computers and other sensitive equipment on the same circuit as the printer, use a power conditioner with Automatic Voltage Regulation (AVR).

Connecting a printer to a line conditioner may prevent the printer from getting the voltage it needs. A better approach would be to have a qualified electrician check the capacity of the existing line and add a separate circuit for the printer if necessary.

What is the difference between voltage fluctuations and a power spike or surge?
A power or voltage spike is a sudden increase in voltage, ranging from a few hundred volts to tens of thousands and lasting between 1 and 30 microseconds. A power surge is like a spike but lasts longer. Voltage fluctuations are normal and do not typically harm equipment connected to an outlet. Over- or under-voltages occur when the voltage reaching powered devices falls out of the normal service range.

Why does my power conditioner make a clicking sound?
As a power conditioner corrects high or low input voltage, it will make a gentle clicking sound. The frequency of the clicking will depend on the quality of the utility power in your area. The clicking is normal, and no action is required on your part.

Should I use a power conditioner or isolation transformer with my guitar amp?
If improved sound quality is your primary goal, an isolation transformer is the best choice. Microphones, instruments and amplifiers can pick up unwanted hums or buzzes if they are plugged into the same circuit as items such as fluorescent lights, air conditioners and dimmer switches. If your band is playing in a bar, even the bartender's blender is a potential source of interference!

An isolation transformer uses two coils of copper wire, wound so that the primary coil connected to incoming AC power induces a current in the secondary coil powering connected devices. Since there is no direct connection between the coils, musical instruments and recording equipment attached to the secondary coil are isolated from audio frequency noise on the power line.

Why Buy from Tripp Lite by Eaton?

We know you have many brands to choose from. On the surface, they may all seem alike. It's what you don't see that makes the difference. With Tripp Lite by Eaton, you get solid engineering, proven reliability and exceptional customer service. All our products undergo rigorous quality control before they are offered for sale, and independent testing agencies verify our products meet or exceed the latest safety and performance standards. Our commitment to quality allows us to back our products with industry-leading warranties and responsive customer service. It's the Tripp Lite by Eaton difference.


Need help with your purchase?
We're always available to help with questions, including product selection, sizing, installation and product customization. Call us at +(773) 869-1776 or email