Light switch installation cost

Installing a light switch costs $120 to $400, typically around $200. Replacing one like for like is $80 to $200. A dimmer is priced similarly; adding a second switch location for the same light is $250 to $700, because that means running a new cable.

The device is $3 to $60. Everything else on the bill is the visit and the access.

What it costs

Because most electricians have a one or two hour minimum, doing every switch in the house in one visit costs a fraction of doing them one at a time. Walk around and make a list first.

Dimmers, and why the wrong one buzzes

A dimmer must match the load. This is the single most common reason a new dimmer hums, flickers, or only works over half its range.

LED needs an LED-rated dimmer, and ideally one the bulb manufacturer lists. Old incandescent dimmers work by chopping the waveform in a way LED drivers dislike, and the result is buzzing, flicker at low levels, and bulbs that will not switch off completely.

Load range matters. A dimmer rated for 150 watts of LED will not behave with 15 watts on it. Many have a minimum load, and a single LED bulb on a big dimmer is below it.

Mixing bulb types on one dimmer makes both behave badly. Use the same bulb model throughout a dimmed circuit.

If a dimmer buzzes, the usual fix is a different dimmer or different bulbs, not rewiring.

Smart switches need a neutral

Most smart switches need a neutral wire in the box to power their electronics continuously. Houses wired before roughly the mid 1980s frequently ran only a switch loop, which means the box has line and switched line but no neutral.

The options:

• A smart switch that works without a neutral, which several manufacturers make and which trickle current through the bulb. They work, and they are fussier with LEDs.
• Running a neutral to that box, $200 to $600, and easy only if the wall is open.
• A smart bulb instead, $15 to $50, which needs the wall switch left on permanently. Fine in a lamp, annoying on a ceiling light other people will switch off.
• A battery-powered smart button fixed over the existing switch, which is the underrated answer in a rental or a house you are not rewiring.

Open the box and look before buying. A bundle of white wires joined at the back means a neutral is present.

Three-way switching, explained once

A three-way circuit is one light controlled from two places: the top and bottom of stairs, or both ends of a hallway. It uses two special switches and a three-conductor cable between them.

Adding a second location to an existing single switch means running that cable, which is why it costs $250 to $700 rather than $150. In a finished wall with no accessible route, it can be more.

The wireless alternative is a smart switch at the existing location plus a battery-powered remote at the second, stuck to the wall. It costs $100 to $200, needs no cable, and it is what most people should do in a finished house.

Frequently asked questions

Can I replace a switch myself?

Like for like, with the breaker off and tested dead, it is one of the more approachable electrical jobs. Photograph the wiring before disconnecting anything. Use the screw terminals rather than the push-in holes on the back, which loosen over time.

Why does my new LED dimmer flicker?

Mismatched dimmer and bulb, in almost every case. Check the bulb manufacturer's compatibility list, use one bulb type throughout, and make sure the total load is above the dimmer's minimum.

What is the difference between a three-way and a two-way switch?

Terminology only. American usage calls a switch with two possible positions in a two-location circuit a three-way; British usage calls the same thing two-way. If you are buying in the US, ask for three-way.

Do smart switches work if the internet is down?

The physical switch always works. The app, the schedules and the voice control depend on the hub or the cloud, depending on the system. Anything using a local hub keeps working; anything cloud-only does not.

Should I put dimmers everywhere?

Kitchens, dining rooms, bedrooms and living rooms benefit. Bathrooms, hallways and utility spaces mostly do not, and dimmers cost more and take up more room in the box.