What is the percentage of houses that has neutral at the light switch?
The percentage for new houses is really high. Old house… Well depend on how many reno and location.
It depends very much on what region you live in. In the UK, for example, I would guess it’s maybe 20%. Which is to say it’s much more common not to have a neutral at the switchbox.
In the US, it was not common to put neutrals at switchbox before 1990. After that, it was common but not required by code until 2011. And not all jurisdictions have fully adopted the NEC code even now.
I don’t think it’s possible to get a firm answer one way or the other as far as total percentages, but in the US, the age of the house is usually what changes the prediction.
Certainly as far as switches being sold, Lutron introduced their Caseta line a few years ago specifically to make it simple for people who didn’t have a neutral at the switchbox but did want a smart switch that could control LEDs to add a smart switch. And that line has sold very well. So I think the market demand is clearly still there.
I’ve done an analysis: