NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

Which of the following HID lamps is the most efficient?

1. HPS

2. MV

3. MH

4. LPS

The correct answer is: LPS

The most efficient HID lamp type among those listed is Low-Pressure Sodium (LPS) lamps. LPS lamps are known for their high efficacy, which means they produce a substantial amount of light for the amount of energy consumed. Specifically, LPS lamps can achieve efficacy ratings of around 200 lumens per watt, making them the most energy-efficient option in the HID category. LPS lamps primarily emit light in the yellow spectrum, which is less appealing for color rendering but ideal for certain outdoor applications such as street lighting. Their efficiency stems from the way they generate light through the excitation of sodium vapor, a process that requires less energy compared to other types of HID lamps. High-Pressure Sodium (HPS) lamps, while also efficient, typically offer lower efficacy than LPS lamps, usually in the range of 100 to 150 lumens per watt. Metal Halide (MH) lamps and Mercury Vapor (MV) lamps have even lower efficacy ratings, often below 100 lumens per watt, which makes them less desirable for energy-efficient lighting solutions. In summary, Low-Pressure Sodium lamps stand out for their efficiency in producing light, solidifying their position as the most efficient HID lamp option among the choices presented.