Why Do Smart Switches Need A Neutral?

Smart Switches must be powered at all times, and without a neutral, that is not possible.

TL;DR: Smart Switches must be powered at all times, and without a neutral, that is not possible.

Why Do Smart Switches Need A Neutral

You've bought a shiny need Smart Switch, ready to bring your home lighting into the 21st century. Breakers' switched off, switch plate removed and screws holding in the switch are removed too. You pull it out and….

There's only two wires attached to the switch (or three if ground is available). Hot in, Hot out and maybe Ground.

But wait? Your new smart switch requires 4 wires. Hot in, Hot out, Neutral and Ground. Will your switch work without a neutral?

Neutral Required

Unfortunately, almost all smart switches on the market require a Neutral wire to operate. Without a neutral wire, it will not function.


The presence of a neutral wire allows the switch to be powered at all times, giving it the ability to stay connected to your home network and stand at the ready for commands. Without a neutral, the switch only has power when the lights are on.

Older homes often have switches that do not contain a neutral in the switch pattress box (the housing the switch installs into), instead they have two wires which form the "Hot" side of the circuit. A regular household switch connects these two wires to complete the circuit:

A neutral connected to the switch completes the circuit, allowing electricity to flow to the switch, even when the lights are off:


Without a neutral, a smart switch will not work. There are a few options to remedy this, including running a separate Neutral to the switch box. Consult with a licensed electrician for options. Improper installation runs the risk of fire, injury or death.

Interestingly enough (and what got me to write this in the first place) is that are a few smart switches out there that do not require a neutral. They do have their limitations though.

Neutral-less Smart Switches

Neutral-less smart switches do exist, but they have their limitations. They work by keeping the lighting circuit connected, allowing electricity to flow through the lights and through the smart switch. Albeit at a trickle flow. By doing so, the smart switch is able to stay powered.

The catch is that because they keep the lighting circuit powered, these switches only really work with old-fashioned incandescent bulbs. Incandescent bulbs require dozens of watts before they start glowing, allowing the smart switch to keep the power flowing without actually making the lights light up.

But newer energy-efficient Compact Fluorescent (CFL) and Light Emitting Diode (LED) bulbs often require only 10 watts or less to operate. The result is constant flickering or glowing from the bulbs when switched off.

The other issue with neutral-less switches is that they require an external hub. This means increased cost to you.

Smart Bulbs

A popular option are Smart Bulbs. These bulbs have all the electronics required to operate located within themselves. The downside to using this bulb is that you would need to keep the switch on at all times so the bulb can receive power. This means you would need to use the app or your smart home device to operate the light. If you accidentally turn off the bulb using the switch, it may take up to a minute for it to reconnect to wifi and be once again accessible.

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