Interlock Vs. Transfer Switch: Which System Is Best For My Generator?

Heather Robbins
by Heather Robbins

What do you do when your power goes out? A standby generator is an excellent piece of equipment to have. After all, this provides electricity to your home in the case of an accident or a storm. Depending on your particular generator, you will have an interlock switch or transfer switch. Both are different in the way they operate.

An interlock switch is a manually operated system. With an interlock switch, you need to set it to the generator setting manually. This ensures that you cannot have the main breaker and generator breaker running at the same time.

A transfer switch is an automatic system. When the power goes out, the transfer switch automatically kicks the generator on. This type of switch also ensures that both breakers cannot be active at the same time.

So which one do you need for your generator? Each generator is different. The switch that you choose needs to comply with the electrical codes. In this article, we will cover how each switch works as well as how to operate them.

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What is an Interlock Switch?

An interlock switch prevents both circuit breakers from running at the same time. You have to manually shut down the main circuit breaker and change it to the generator for power supply.

How Does An Interlock Switch Work?

When you have a power outage, you have to move the interlock switch. You make the switch from the main breaker to the generator breaker. There are a few additional steps you need to take to keep safety a priority.

Here is the interlock switch process in the event of a power outage:

  • First, you must cut the power to all circuit breakers.

    This is because generators can produce large amounts of carbon monoxide. You do not want the power to the generator until it is running smoothly.

  • Secondly, you set the interlock switch to ‘generator.’

    After you change the setting, turn your generator on. Let it run for a few minutes before turning the primary circuit back on.

  • Third of all, you will not want to turn the power back on to the main circuit breaker.

    Turn off the individual breakers that you don’t need. For instance, if you’re not using the living room, turn off that breaker.Cutting off any necessary circuits can help your generator not work as hard.

Interlock Switch: Pros and Cons

In What Situations are Interlock Switches Best?

The use of interlock switches vary within a variety of settings that include:

  • Residential homes
  • Smaller businesses
  • Any place where someone knows to operate the switch safely

These buildings are smaller; therefore, an interlock makes sense.

What is a Transfer Switch?

A transfer switch will automatically switch to a different power source in the event of an outage. The transfer switch will start the generator on its own. When the power restores, the transfer will switch back to the main power supply.

How Does a Transfer Switch Work?

The dynamics of a transfer works the same as an interlock. A transfer switch ensures that the primary circuit and generator’s circuit cannot run at the same time. The only difference is that it does it automatically.

There are no extra steps aside from checking that everything is right. The transfer switch even goes as far as detecting the power outage.

If you get a more intricate transfer switch, you can control it from your phone or computer! You can also set it up to get notices of outages. That way, if you’re on vacation and have a house sitter, you don’t need to explain how to operate an interlock switch.

Transfer Switch: Pros and Cons

In What Situations are Transfer Switches Best?

Transfer switches are more common in commercial buildings. Or, other places where they need to have access to power such as:

  • Commercial refrigeration buildings for food
  • Hospitals/Nursing homes
  • Factories
  • Large warehouse grocery stores
  • Any place where someone would rather have an automatic process

It’s not unheard of for residential homes to have transfer switches. Whether or not you use an automatic process depends on your budget.

Prices: Interlock Switch vs. Transfer Switch

Prices of these types of switches differ depending on the amp and voltage that you need.

Interlock Switch Prices

Here is a chart with a few different pricing options:

Prices for Interlock Switch

Siemens Heavy Duty Indoor Fusible Safety Switch with NeutralSiemens General Duty 2-Pole Outdoor Fusible Safety Switch with NeutralSiemens Heavy Duty Pole Outdoor Fusible Safety SwitchSiemens Heavy Duty 3-Pole Type 4X Non-Fusible Safety SwitchSiemens Heavy Duty 3-Pole Type 4X Non-Fusible Safety Switch
Price$76 – $80$108 – $112$210 – $215$795 – $800$1,080 – $1,100

As you can see, the prices for interlock switches dramatically vary depending upon your personal needs. If you’re using interlock for a small home, you will pay under $200.

Transfer Switch Prices

Here are a few different products just to get an idea for prices of an automatic switch system:

Prices for Transfer Switch
Reliance Controls Non-Fuse 6-Circuit Transfer Switch Kit Generac Automatic Start Transfer Switch with Power ManagementGenReady Automatic Transfer Switch w/ power managementPower Command Automatic Transfer SwitchHoneywell RTSZ Model Transfer Switch
Price$280 – $285$590 – $610$1,030 – $1,060$1,950 – $2,000$5,190 – $5,220

As you can see, the price difference is pretty extreme. Although, the $600 range and up have a way to control your switch remotely. The price depends on the number of amps you need, as well as the conveniences you prefer.

Always be sure and check the requirements for the switch you need. Also, make sure your switch is compatible with your generator. Ideally, you will have an electrician come out before you buy your switch. They can tell you which type you need and what requirements they should meet.

Switch Installation: Can You Do It On Your Own?

Installing a switch for your generator should never be done on your own. It may even be illegal to do that where you are. The reason it is illegal in some areas is because of safety concerns.

If you make one wrong move, you could electrocute yourself or someone else. You could start a fire. Or, you could completely ruin the power supply to your home. Instead of taking that risk, it’s better to hire an electrician to do the job for you.

Also, an electrician needs to come to see your generator anyway. They are the only ones that can tell you if you can use a transfer switch or interlock switch. Also, they are the only ones who can you if everything is up to code compliance.

Although it will cost you less if you polarize your generator yourself! Now that, you can do.

How Much Does it Cost to Hire an Electrician to Install Everything?

The price of hiring an electrician is highly circumstantial. If this is a job for a larger business, then the cost is going t be on the higher end. However, for your home, it will most likely fall between $200 to $400.

For your private home, the installation price depends on the complexity of the installation as well. In turn, the complexity depends on the conveniences included, and the size of your home.

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Related Questions

Can You Run a Generator Without A Transfer Switch?

Technically, you can run a generator without a transfer switch, although this is extremely dangerous. Plus, it limits what your generator can power throughout your house. This is not ideal especially if you have a smart home. In addition, if you do not put a switch on your generator, you risk extreme power surges. A power surge could fry appliances, and not to mention, cause fires. You might as well avoid the hassle of it all and just put a switch on your generator.

How Do You Make a Generator Transfer Switch?

Steer away from creating a transfer switch on your own. This is especially dangerous if you have no idea what you’re doing. When taking on projects such as these, it’s better to leave it to a licensed professional.The damage a fire would cost you will far surpass the amount for an electrician and a switch kit.

Heather Robbins
Heather Robbins

Heather is a passionate writer who loves anything DIY. Growing up, she learned everything from home repairs to design, and wants to share her tips with you. When she's not writing, she's usually hiking or searching for her next DIY project.

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