20 Watt can be too much

Usually LEDs are installed because they are more efficient than traditional street lights. This means you get considerably more light for the same wattage. Andrej Mohar from Dark Sky Slowenia has an example of what happens, when this efficiency is underestimated.

The light in the picture comes from a 4000 Kelvin LED street light with 20 Watt put on an eight meter lamp post. You can see the shadow of this post in the picture.

According to Slowenian law, only luminaires with ULOR 0 are allowed, that means no light is allowed to shine above the horizontal level. This is also the case in this street light, but it still illuminates a huge area of field and the far off buildings. The residents of the village seen in the back of the pictures complained immediately after the light was installed.

If you look at coverage and intensity of this light it is obvious that 20 Watt are way too much for an LED street light. Five or 10 Watt would probably be enough, with a maximum of 3000 Kelvin. However, the industry is currently producing LED lights with 70 Watt and more. This will cause even more light pollution, more energy consumption, and more glare for drivers.