Interlock vs Transfer Switch for Generator: Which Is the Best


When considering backup power solutions for a home, choosing between an interlock and a transfer switch is a pivotal decision. Both are designed to ensure a safe transition of power sources, but they operate on distinct principles. 

Each option presents its own set of benefits and considerations, so choosing the best one often boils down to individual needs and circumstances.

What Is an Interlock?

An interlock is a straightforward yet highly effective device that facilitates the safe operation of a generator in tandem with your home’s electrical system. Acting essentially as a safety mechanism, it ensures that only one power source – either the main utility power or the generator – can be active at any given time. 

The primary objective of an interlock is to eliminate the risk of backfeed, a dangerous situation where electricity from the generator flows back into the main power lines. Such a situation could pose significant risks, including potential electrocution hazards for utility workers. Using an interlock allows homeowners to easily switch between power sources, ensuring a reliable and safe energy flow during power outages.

What Is a Transfer Switch?

A transfer switch is a pivotal component in power management, enabling a seamless and secure shift between the main utility source and a backup generator. Its primary role is to guarantee that both the utility power and the generator aren’t connected to a building at the same time, averting potential risks. 

We cover the different types of transfer switches below:

Manual Transfer Switch

The Manual Transfer Switch (MTS) calls for human intervention. When power outages occur, an individual must manually alternate the power source from the main grid to the generator. This type is commonly chosen for more modest settings, such as homes or small enterprises. 

Non-Automatic Transfer Switch

There are also non-automatic transfer switches, which are electrically operated switches. While they can’t self-initiate in the event of a utility outage, these are a convenient choice when the transfer switch isn’t easily accessible.

Automatic Transfer Switch

The Automatic Transfer Switch (ATS) functions without manual oversight; it can detect a loss in utility power, promptly switching to the backup generator. Once the main power is reinstated, it seamlessly reverts. Such automation makes the ATS a favored choice for environments like hospitals and data centers.

How Does an Interlock Work With a Portable Generator?

An interlock is a brilliant solution that acts as a bridge between a portable generator and your home’s electrical panel. When the power goes out, and backup is needed, the interlock system safely connects the generator to your household circuits, ensuring that only one power source is active at any given time.

The working principle is straightforward. When the grid fails, you manually slide the interlock plate, turning off the main utility breaker and enabling the generator breaker. This prevents the dangerous back-feed to the grid and ensures power only flows from the generator. 

For those seeking a user-friendly, budget-conscious solution, interlocks paired with portable generators can be a game-changer.

How Does a Transfer Switch Work With a Portable Generator?

Transfer switches are critical in maintaining a smooth transition of power from the main grid to a generator during outages. When the utility power falters, a transfer switch springs into action. A key advantage of a transfer switch is its ability to manage power distribution efficiently, directing energy only to essential circuits reducing generator load. 

Safety is another benefit of transfer switches, as they prevent backfeed to the grid, which can be hazardous to utility workers and the neighborhood. As blackouts become more frequent, integrating a transfer switch with a reliable portable generator is more than just a convenience – it’s peace of mind. With an innovative power solution integrating a transfer switch, like EcoFlow’s EcoFlow DELTA Pro + Transfer Switch, you can ensure you’re always a step ahead of power interruptions.

Here are expert tips for installing EcoFlow Transfer Switch for Delta Pro

What Are the Key Differences Between an Interlock and a Transfer Switch?

1. Purpose

The core purpose of both devices is to ensure safe generator connectivity. An interlock is a simple mechanical system, acting as a manual slide or a barrier, ensuring that the main breaker and generator breaker cannot be on simultaneously. On the other hand, a transfer switch is a device that automatically or manually switches between utility and generator power.

2. Installation

Interlocks are generally easier to install compared to transfer switches. They’re installed directly on your home’s electrical panel. Transfer switches, especially the automatic variants, require a more intricate installation process, often demanding dedicated circuits.

3. Cost

Interlocks are generally more cost-effective. They’re simple devices and don’t require elaborate setups. Transfer switches, particularly the automatic ones, can be pricier due to their complexity and the advanced features they offer.

4. Safety

Both devices offer safety measures, but their mechanisms differ. Interlocks prevent dangerous backfeed by ensuring that only one source (utility or generator) can feed the panel at any given time. Transfer switches inherently prevent backfeed and can also offer advanced features like automatic activation upon detecting power loss, ensuring a seamless transition.

Frequently Asked Questions

Which Is Better, an Interlock Kit or a Transfer Switch?

Both interlock kits and transfer switches have their advantages. Interlock kits are simpler, cost-effective, and easier to install, making them ideal for occasional use, while transfer switches, especially automatic ones, are pricier but can offer seamless power transitions and greater safety features. Your choice should be based on your usage frequency, budget, and desired level of convenience. Make sure to also comply with applicable laws and codes.

Can I Use an Interlock Instead of a Transfer Switch?

Depending on your circumstances, an interlock may be used as an alternative to a transfer switch. It ensures that the main and generator breakers can’t be turned on simultaneously, preventing dangerous backfeed. However, while interlocks provide basic safety, transfer switches offer additional features, especially in the realm of automatic power transitions during outages.

What Is the Alternative to a Generator Transfer Switch?

The primary alternative to a generator transfer switch is an interlock kit. It provides a manual method of switching between utility and generator power. While it doesn’t offer the seamless transition of an automatic transfer switch, it’s a cost-effective solution that still maintains essential safety measures. Depending on your circumstances, you may be able to use an interlock kit instead of a transfer switch.

Is a Generator Interlock Kit Necessary?

In order to use a generator safely, you need an approved switch that’s been installed according to electrical codes, whether it’s a transfer switch or an interlock. Without an interlock or transfer switch, you risk damaging equipment, causing fires, or endangering utility workers. Make sure you’re in compliance with applicable laws and codes.

Final Thoughts

Choosing between an interlock and a transfer switch for your generator involves weighing cost, convenience, and safety. Interlock kits provide a cost-effective solution, ideal for sporadic use, while transfer switches deliver enhanced safety and smooth power transitions. Both aim to ensure a safe integration of generator power with your home’s electrical system. 

As we embrace more sustainable and reliable power solutions, it’s vital to have the right equipment for your needs. If you’re leaning towards the more advanced features that come with a transfer switch, check out our transfer switch today.

To explore innovative solutions and tools that elevate your energy setup, consider our offerings from EcoFlow. With extremely portable solutions like the EcoFlow RIVER 2 series all the way to whole home generators, you’re sure to find your ideal power solution. 

EcoFlow is a portable power and renewable energy solutions company. Since its founding in 2017, EcoFlow has provided peace-of-mind power to customers in over 85 markets through its DELTA and RIVER product lines of portable power stations and eco-friendly accessories.

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