LED streetlights are great for the environment. They consume much less energy than standard high-intensity discharge (HID) lights, last three times longer, and they reduce greenhouse gas emissions and maintenance costs. In general, LED lights also contribute less to light trespass because they emit direct illumination. Because of all their great qualities, many cities have started to convert from HID to LED streetlights. What some cities have failed to consider, however, is that while LED streetlights are capable of emitting different colors of light, not every color should be used in public outdoor spaces. Bright blue-rich white light can cause some issues for residents, local wildlife, and night sky visibility. When it comes to streetlights, the warmer the color/correlated color temperature (CCT) the better.
CCT will tell you what hue and tone of white to expect from a specific streetlight. It is measured in Kelvin (K), which is similar to degrees in Celsius. Different temperatures on the Kelvin scale represent different colors. For example, light at 2000K-3500K looks more orange/yellow and is called ultra warm or warm white, and as temperature increases in Kelvin, color changes to more of a “paper white” known as natural or neutral white (between 3500K and 5100K) and finally into a bluish-white known as cool white (5100K-20000K).Because blue light has a larger reach, cool white LED lights used outdoors at night can contribute to light pollution, or brightening of the sky. This decreases the visibility of stars and can have a negative effect on astronomical research. If cool white LED lights are used, they should be shielded or aimed directly downward to prevent light pollution