Do I need an add-on switch? What is the purpose of the add-on switch?

I don’t know why I am having such a tough time figuring this out but can someone explain this to me like I am a 5 year old.

What is the main purpose of a add-on switch?

I have a four switch outlet in my entry way and I want to put a GE smart switch to replace one of them to automatically control my exterior lights. I don’t need smart switches for the other three but I do need to replace them to make them all rocker switches. Can I just put regular switches in those other three spots or do I have to use add-on switches?


The add on switch is when you have a 3-way setup where 2 switches control the same lights/outlets. One switch is the full fledged smart switch and the other is a dummy add-on switch that talks to the main switch.

You can put regular old rocker switches in the other spots

That makes a lot of sense. I don’t understand why it wasn’t clicking for me.

I still don’t quite get this. Why would you want to control the same switch/outlet with 2 switches?

This has nothing to do with home automation, it’s very common in a house that has large rooms with multiple entrances.

For example, if you have a kitchen where there is one door that goes to the garage but you can also enter from the other side, maybe from the hallway, it’s pretty common to have a switch on each side of the kitchen that each controls the same overhead light.

You’ll also get this on stairways, where there will be one switch at the bottom of the stairs and another switch at the top of the stairs, and they both control the same light.

Or at opposite ends of the long hallway.

When I was a kid, I lived in a house that had a dining room with an entrance on one side from the living room, and an entrance on the other side from kitchen. Again, there was a light switch by each entrance that each controlled the same overhead light.

So multiway switches are just a convenience for rooms with multiple entrances, or areas like a staircase where you may want to be able to control its light from two different locations.

There is now an FAQ on add on switches. :sunglasses:

Thank you @JDRoberts - totally cleared that up. You are the bomb! :slight_smile: :apple:

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Hey there.
So I am still a little lost. I completely understand what the add on switch is used for, however, I don’t understand why one would buy an add on switch. I have multiple 3 ways in my home. Let’s take the stairway for example… currently I can turn the light on and off from upstairs and downstairs. Say I install a on off smart switch downstairs, why would I need an add on for upstairs? Would the regular switch upstairs no longer work? As far as automation is concerned, I will be able to turn the light on off from my phone, Alexa etc as the downstairs now has a smart switch. Why does one need an add on? I hope someone can help. Thanks a ton!!

Networked switches are typically wired somewhat differently the non-network switches so when you replace one switch in a three-way you have to replace them all. It’s not so much that the upstairs Switch would no longer work, it’s that flipping the upstairs Switch might then cause the downstairs switch not to work. The wiring pattern is just different. See the FAQ

And, yes, you’ll be able to turn the master switch on and off from your phone or by voice if you have a device like an Amazon echo. The second switch is just a convenience. If you want to get rid of it you can blank it off, you just can’t leave the old one in place.