How Does A Generator Transfer Switch Work?

How Does A Generator Transfer Switch Work

When buying, hiring or using a generator you will see that many makes and models include a transfer switch. In case you are unsure as to whether you need a transfer switch, or what type of transfer switch you need as well as why you might need one, we’ve covered everything you need to know in this brief but informative article. 

What Is A Transfer Switch? 

A transfer switch is an electrical switch that transfers the power between a generator and the main grid supply in a residential, commercial or other building.

Manual vs Automatic Transfer 

Some generators have an automatic transfer switch so when the mains supply from the grid fails, the generator automatically transfers the mains power to that made by the generator and switches the generator on.

Generators that have a manual transfer switch require someone to manually switch the power from the grid to the power from the generator. 

How Does It Work?

The generator transfer switch is connected to the mains electricity as well as the load it is supporting. It only completes one of those circuits at a time, making it impossible for both to be connected at the same time, preventing back feed into the grid and potential overload of the appliances within the home/building. 

Why Do You Need One?

A transfer switch is a safety device. You need one for the following reasons:

  • Having power from both the generator and the mains running into your appliances at the same time will overload them risking irreparable damage and fire. 
  • Transfer switches prevent back feed from the generator from going into the grid – this is potentially fatal for those working on powerlines. 
  • If you have important equipment, appliances or devices that cannot be switched on, an automatic transfer switch will ensure a generator takes over seamlessly – in a hospital, for example, an automatic transfer switch is essential.  
  • Using a generator that can plug into your mains is not only more useful, but is essential for many household needs such as heating/hot water, lighting, water pumps and any appliances that are connected directly to the mains electricity. It is also safer than having long cables and extension leads running through the house causing trip hazards and other risks. 

What Generators Need A Transfer Switch?

Only residential, commercial and other generators that are plugged into the mains require a transfer switch. It doesn’t matter which type of generator fuel is being used, however, it is generally recommended that any generator over 5000W has a transfer switch. 

So, generally speaking, portable generators such as those you use for camping generators or your on-site power tools will not require a transfer switch. 


For seamless backup power to your commercial building or your home, a transfer switch is not only a useful addition but an important safety feature. 
To find out whether you need a generator with a transfer switch and whether a manual or automatic one would best suit your needs, get in touch with our experts here at Generator Pro. Don’t forget to browse our excellent range of generators online including those with manual and automatic transfer switches.

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