We interact with streetlights every night. We probably think nothing twice of the light they provide. However streetlights contribute to a vast majority of light pollution in cities. This streetlight is a high pressure sodium (HPS) light. Although the soft orange glow is preferable for our eyes over the harsh white glow of new LED streetlights, the HPS light uses more energy. These are a type of gas-discharge light where a gas mixture is ignited by an electric discharge. While these lights last around 24,000 hours, when they start to burn out, it takes more energy to light them. Cities are now beginning to replace HPS lights with LED lights which offer tremendous cost savings. However it is quickly becoming apparent that LED lights are not the heroes we make them out to be.
International Dark Sky Association - Phoenix Area Chapter 