For UK homes it was around 10%-15% for lighting. It varies considerably based on the type and quantity of lighting installed and whether the property uses electric heating or some other fuel.
Incandescent to LED will cut lighting energy use by at least 90%, and around 95% for the latest types of LED, which will make lighting only 1 or 2% or so with no other changes.
For non-domestic, lighting is usually a lot more, 20%+.
However the savings for LED compared to incandescent are vast regardless of what percentage of the total lighting is.
A 100W lamp used for 1000 hours is about £27 of electricity - less than 3 hours a day for a year
a 10W LED only £2.70, saving over £24. Newer LEDs are only 6W or so for the equivalent lumen output.
The same applies to commercial installations but with much larger savings, which is why huge numbers of commercial locations changed to all LED years ago.
The change to LED lighting and the compact fluorescents before them is one of the main reasons why electricity consumption in the UK has been falling almost every year for the last 15 years.