Last updated: 16/10/2022

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Welcome to ReviewBox Brasil! Today we are going to talk about an accessory that is always useful at home or in the office: the extension cord.

Ideal for connecting various appliances to the electric power, especially in the absence of nearby sockets on the wall, the extension cord is one of those devices that you need to have around.

Today there is a wide variety of extension cords and, therefore, we will show you in this article what you should check before buying the best model. that will meet your expectations and needs.


  • The extension leads displace and multiply the number of sockets so that you can connect several appliances at the same time, wherever you want.
  • There are several models of extension cables, but you need to be careful because not all electronic equipment should be plugged into this accessory.
  • We will show you which characteristics differentiate one model from another and how to choose the ideal extension cable.

The Best Extension: Our Picks

Buying Guide

It may seem simple enough to choose the best extension cord. But as there are variations in models and cable lengths, a little more thought is needed before you can buy the right one.

That is why we have created this Buying Guide with all the information you will need to make the best decision when buying the best extension cable.

Mão plugando tomada na extensão.

The extension cord is a practical and functional accessory for use at home or in the office. (Source: Antonio Guillem /

What is an extension cord?

You’ve probably had trouble plugging in a lamp, a mobile phone charger and a lamp at the same time for lack of sockets nearby. Or even because the wall sockets were too far from where you intended to plug them in.

Situations like these occur frequently in any home and especially in offices.

To solve this problem is that extensions arise. Also known as electrical extension, ruler or power extension, the extension is a device that displaces and multiplies the number of sockets.

With this, you can use various equipment that depend on electricity, anywhere, and at the same time. For this, you only need one socket on the wall.


The extension allows you to plug in multiple appliances at the same time with just one wall socket. (Source: Erkki Makkonen /

Generally speaking, the extension cord is a device formed by a base that contains sockets, where the appliances will be connected, plus an extension cable that will be plugged into the wall socket.

Some extension leads can connect more than 16 appliances.

Nowadays there are several extension lead options, with different designs, number of sockets and extension cable length. You will find from the simplest extension models, with a small number of sockets, to the most complete with options to connect more than 16 appliances.

What is the difference between an extension cable and a line filter?

You must be careful not to confuse the extension with the line filter. Although both look similar, with a base, sockets and cable, these devices have different functions and objectives.

As we have seen, the extension cord is used so that you can connect several appliances at the same time in the absence of sufficient sockets in the nearest wall.

But the extension does not offer any protection for your appliances in case of a power overload.

Mesa com pessoas usando notebook, e extensão elétrica.

Unlike the power strip, the extension cord does not protect against a power surge. (Source: rawpixel /

The line filter, on the other hand, despite also multiplying the number of sockets, has the function of protecting the appliances connected to it.

The line filter identifies when an overload or short circuit occurs in the electrical network. And, in this way, it is capable of interrupting the power before it can damage the equipment that is connected to it.

To stop excess power, some models of line filters have circuit breakers and others have a fuse.

The circuit breakers just cut the power in case of problems. The fused power strip retains excess electricity.

The line filter makes sure that the right amount of electricity reaches your appliance, preventing appliances connected to it from burning out.

In short, when you just need to move and interconnect your equipment, the best option is to buy an extension cord.

But if you need to connect your equipment and also protect it against voltage surges, we recommend that you choose a line filter.

Also, in general, a power strip is more suitable for connecting appliances with a higher power, such as microwaves, refrigerators, and hair dryers.

See below the table showing the main differences between an extension cable and a power strip:

Extension Line filter
Function Connect and move several appliances at the same time in the absence of sufficient or nearby sockets on the wall Multiply the number of sockets and protect the connected appliances against electrical discharges and overloads
Number of plugs Greater variety Less variety
Extension of the cable Larger Smaller
Ideal for Appliances of lower power Appliances of higher power

What are the safety recommendations for using the extension cable?

Like all devices that transmit energy, the extension cable can also offer risks if used incorrectly.

This is because with the increase in the number of appliances connected to the same source, overloading and short circuits can occur, which can permanently damage your electronic equipment.

Not to mention the imminent risks of fire. So, check out the following tips from experts for you to use the extension cord safely at home or at the office:

  1. Use quality products: When the cables, plugs, and sockets have quality, they help prevent fires and electric shocks.
  2. DR: Ideally, extension cords should be plugged into sockets protected by a DR (residual device) which automatically shuts down the circuit when it detects a current leakage.
  3. Power: The sum of the currents consumed by the appliances connected to the extension lead should not exceed the maximum capacity of the wall socket. For a standard residential socket, the limit may be 10 or 20 amperes (A).

Mão plugando tomada na extensão.

Attention is needed when using the extension cord to avoid accidents. (Source: /

In addition, we also list below two important recommendations from the National Institute of Metrology, Quality and Technology, Inmetro:

  • Never use an extension cord with a built-in wire. If you choose an extension cord with a built-in wire, you should only use the extension cord with the cable fully unwound. Otherwise, the extension cord may catch fire.
  • Do not buy extension cords from the informal trade. This is because most of these products are made from scrap or are of foreign origin. According to Inmetro tests, this type of extension cord has the worst performance.

What are the advantages and disadvantages of the extension?

There are many advantages to having an extension cord, whether at home or at work. The fact is that the extension cable is a practical and useful accessory that solves the problem of lack of sockets.

In other words, when you need a power outlet nearby but do not have one, the extension cable allows you to connect several appliances at the same time in the desired location.

Besides, the extension cord is a versatile product. As it comes in a wide variety of models, numbers of sockets and different cable lengths, you can choose the one that best meets your objectives.

Extensão com seis tomadas ligadas com aparelhos diferentes.

The big advantage of the extension cord is that you don’t have to rely on multiple wall sockets. (Source: olegdudko /

For example, with the extension, you can plug in a lamp, a desk fan and a phone at the same time, with only one socket on the wall.

As these devices have low power consumption, they will not exceed the current capacity of the socket.

On the other hand, with appliances that consume more power, the extension cord would not be safe.

Another disadvantage is that the extension cord if used improperly, can cause fires and damage electronic equipment connected to it.

Below, you check out the main advantages and disadvantages of the extension cord:

  • Displaces and multiplies the number of sockets
  • Variety of models and quantity of plugs
  • Short or long extension cable
  • Does not protect against energy overload
  • Risk of fire and short circuit
  • Functional only for low energy consumption appliances


Purchase criteria: What to consider before buying an extension

As we have already mentioned, there are several extension lead options for sale. For you to invest in the most suitable electrical extension you need to consider both your purpose of use and the properties of each model.

That’s why we have selected for you the main factors you should check before buying the ideal extension:

  • Extension cord format
  • Number of sockets
  • Type of pins
  • Cable length

Below, we will explain each of these factors for you to make the best decision and buy the best extension.

Extension cord format

First of all, you should look at the shape of the extension. In general, you will have two options here: the round extension and the long, rectangular, ruler-shaped extension.

The round extension has the advantage of being more compact and discreet. On the other hand, this model has fewer sockets.

In addition, it is very common to find a round extension cord with a retractable cable. This feature is also practical, especially when storing the extension cord, without having to worry about the wire.

Pessoa com notebook e extensão elétrica.

The extension in the ruler format is more modern and can have more sockets. (Source: rawpixel /

However, as we pointed out, for safety reasons, you should only use the extension cord with the whole cable stretched out.

Already the extension in ruler format is more modern and, in general, has a larger number of plugs. As it is thinner, despite being more apparent, this type of extension takes up less space.

See below the main differences between the extension formats:

Round extension Ruler extension
Advantages Compact, easy to store and may have retractable cable More modern design and higher number of sockets
Disadvantages Fewer number of sockets May take up more space

Number of sockets

Also, observe the number of sockets available on the extension cable. To choose the right one, take into account your usage needs.

In other words, evaluate the quantity of equipment that you will need to plug into the extension at the same time. A good strategy is to consider one or two more sockets than you really need.

The more outlets for connecting different appliances, the more functional the extension cord will be.

For example, if you need to connect an alarm clock and a mobile phone charger near your bedside, we recommend that you opt for a four socket extension lead as a guarantee.

After all, it’s likely that at some point you’ll also want to plug in a light fixture, for example.

In general, you can opt for electrical extensions that contain between one and 16 sockets.

Type of pins

Another factor you should check is the pin type of the sockets on the extension lead. The most common is that the sockets are suitable for 2P +T pins, i.e. the well-known three-pin socket.

But you can also find the extension cable for two-pin plugs and even universal plugs.

Cable length

Finally, take into account the size of the cable. This is an essential factor if you need to connect appliances that are very far from the socket that is on the wall.

You will find extension cords with different cable lengths, which can vary between 1 meter and 50 meters.

But, as we have seen, the extension cable for use in companies and offices can have an extension cable of up to 100 meters.

(Source of the highlighted image: byrev /