Low and high-pressure sodium lights are found in parking lots and areas where security is important. The lights require up to 10 minutes to start and are best used when they can stay on for hours at a time. There are several differences between low and high-pressure sodium lights.
Low-pressure sodium lights produce the greatest amount of light per watt of energy consumed. High-pressure lights are slightly less efficient. The efficacy in lumens per watt for low-pressure sodium lights is 60 to 150; for high-pressure lights it is 50 to 140.
High-pressure sodium lights have a better color rendition than low-pressure sodium lights. The high-pressure lights produce a more desirable golden to white light, while the color produced by low-pressure lights is yellow to orange. High-pressure sodium lights are more popular than low-pressure lights because of this significant color difference.
The expected lifetime for high-pressure sodium lights is longer than low-pressure sodium lights. High-pressure lights have a life expectancy of 16,000 to 24,000 hours while low-pressure sodium lights should run for 12,000 to 18,000 hours.