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Making the Right Choice: Transfer Switch vs. Interlock

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The utilization of generators nowadays is very popular. There are households and businesses, either big or small, that invest in this kind of application. It saves the user from spending money on electricity bills. There are many different types of generators, and they all have different functions as well. However, what’s common is their function of supplying backup power. This article will focus on the comparison of interlocks and transfer switches in generators. If you currently have a generator or are planning to have one in the future, then this could be helpful to you.  

What is A Transfer Switch?

To better understand, let us first identify what a transfer switch is. It is also called a transfer panel and it is a device that allows a smooth transfer of power source. When the first source (main grid) suddenly becomes unavailable due to power interruption, the supply of power will be transferred to the backup generator. Additionally, transfer switches ensure that the operation would not harm the electrical equipment and the devices connected to it. This works automatically or manually depending on what type will suit your needs and will operate in a controlled manner that prevents chaotic changes in the electrical supply.

The transfer switch lies between the main source of electricity and the backup. The technology behind the transfer switch is quite simple to perceive. It is designed to basically act as a switch to decide where the source of electricity will come from.

This can be used in various settings such as data centers, commercial buildings, small businesses, and even residential areas.

Quick Guide to Using Transfer Switch

The transfer switch can be operated in different ways. It can be through Manual Transfer Switch (MTS), Non-Automatic Transfer Switch, or Automatic Transfer Switch (ATS).

Manual Transfer Switch requires human action literally, wherein the user would have to control breakers and switches. When an outage occurs, the user manually transfers the power source from the main grid to the backup. This type of transfer switch is usually used in small applications like residential use.

A non-automatic still requires human action to initiate the process. It functions through its internal system equipment and operates the transfer by electric operation. An electronically operated device triggers the switch and the decision on when to activate the switch lies in the user’s hand. Non-automatic is best applied when there are multiple transfer switches that need to be operated.

The Automatic Transfer Switch can work entirely on its own, it works through its programmed system. Once a sudden change in the power supply has been detected, it will smoothly change the power source from the primary source to the backup.

It is important to note that these will operate at their best when they are compatible with your setup and installed properly. A company named Growatt, is a brand popular in manufacturing solar generators for home backup power and is compatible with transfer switches. It offers advanced features that ensure smooth operation in case the grid is unavailable.

What is an Interlock?

Contrary to the transfer switch, an interlock does not function automatically. Instead, this is manually operated. It is also said that this is an alternative to the transfer switch. This is designed for the main grid and generator to prevent both from operating at the same time.

Interlocks are important because they prevent the generator from back-feeding, reducing the harm it may cause to the equipment and the operators.

How Does an Interlock in Generators Work?

transfer switch - Growatt

Since an interlock is something that you need to control by hand, when the main grid goes out, you need to move the switch from the main power to your backup (generator). Before that, you need to turn off the main breaker and all the other switches. Once the switch has been set to your backup, it is time to start the generator and turn on once again the main breaker to power the electrical panel. After that, you can turn on individual switches for your specific needs.

Choosing Between Transfer Switch and Interlock: Factors to Consider

The most important things that a user considers in making choices are its cost, safety, and convenience.

Cost (budget)

In terms of cost, interlocks are simple and do not require complicated setups making them less expensive compared to transfer switches. Transfer switches provide more advanced features that make them cost more than Interlocks. If you want the cheaper option, it should be the interlocks but if you want something that caters to all your needs and is cost-effective, you may choose the transfer switch.


When it comes to safety, both Interlocks and Transfer Switches offer safety measures. Transfer Switches are automatic ensuring smooth processes, while the Interlocks require careful handling so the user does not commit errors that may lead to damage. Transfer Switch is the best choice when you want assurance of your safety while being convenient.


As mentioned above, interlocks are operated manually, and transfer switches are automatic. For example, if you are away from home when a power outage occurs, if you have a transfer switch, the power supply will be uninterrupted, but if what you have is the transfer switch, operating it without human intervention would not be possible.


Interlocks apply to small-scale applications such as portable power stations or backup power and low-wattage appliances at home. Whereas transfer switches are for bigger applications like data centers and industries that use generators. This is because of the advanced feature that transfer switches have. It is capable of serving applications that require big amounts of loads. However, you may also use transfer switches in small-scale applications such as home backup just based on its features alone.

The Role of a Transfer Switch (Purpose)

When you currently have an installed backup power such as generators, it is good to consider having transfer switches, but why are transfer switches helpful, and why do they seem important to most users? Having a transfer switch ensures the safety of the user and lessens harm to the electrical system. With this, all the critical functions that go between the main grid and the backup power will be done conveniently and more effectively. Additionally, huge loads carry more current and can be dangerous not just to the device but as well as to the user.

It is strongly suggested that backup generators for residential and commercial purposes should have transfer switches so that when a power outage unexpectedly occurs, the supply of power will keep going and reduce downtime. Since it is capable of carrying big loads, this is not just used in residential areas. It is best applied in industrial setups and applications that should not have interrupted power supplies.

interlock - Growatt

Making Your Choice: Final Thoughts

There are a lot of factors that affect the decision in choosing between transfer switches and interlocks. First on the list is the cost, followed by its features. Individual users have different requirements depending on the needs of their installation. In choosing the most suitable transfer switch for your application, take note of its amperage, ratings, and voltage. 

In terms of large applications, transfer switches should be applied but when it comes to small ones, interlocks would be fine.

Overall, transfer switch and interlock provide the same service, which is to ensure the safety of the user, to reduce the risk of dangerous occurrences, and more. In the end, your choice should be based on your need or the need of your application.

It is important to keep in mind that in making your choice, what you must see to it is the need for your equipment. If unsure, you may consult an expert regarding this matter or do careful research. Devices also come in user guide manuals that can be reliable.

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