After calculation and when in 3D view, you can go to the false color display to choose either illuminance, lux or luminance cd/m2 to simulate it in your area. You also have the freedom to assign a color to your value.
This is a very clear way of explaining to your client the lux levels present in a given area rendered.
The good thing is that the false color display will appear both on your 3D render view and in your print out once selected.
Try it now.