Lux (Illuminance) is a measurement of the light intensity at any point. It is equal to 1 Lumen per square meter. In Solar Street Light It is difficult to give you exact LUX because of spread on light. It also depends on the height of installation and with each angle LUX changes.
How to measure the Lux for a light?
A light meter is used to measure the amount of light distributed over a particular area at a specified distance from the light source. The units that a light meter will measures in are either Lux, lumens and/or foot candle.
Below is the calculation for a 20 Watt Solar Street Light: