Luminous efficacy - (symbol: lm/W)

Luminous efficacy is a measure of how efficiently a light source produces visible light in relation to the amount of energy it consumes. It indicates how effectively a light source can convert electrical energy (or other forms of energy) into visible light that the human eye can perceive. Luminous efficacy is typically expressed in units of lumens per watt (lm/W).

In simpler terms, luminous efficacy tells you how much light output you can expect for a given amount of energy input. A higher luminous efficacy value indicates that a light source is more efficient at producing visible light, which is desirable for energy-efficient lighting solutions.

Different light sources, such as incandescent bulbs, fluorescent tubes, LED lamps, and even natural light sources like the sun, have varying luminous efficacies. For example:

• Incandescent bulbs: These have relatively low luminous efficacy, typically around 10-20 lm/W. They produce a lot of heat along with light, which makes them less efficient.
• Fluorescent lamps: These are more efficient than incandescent bulbs and generally have luminous efficacies ranging from 50 to 100 lm/W. They produce light by exciting a phosphorescent coating with ultraviolet radiation.
• LED lamps: Light Emitting Diodes (LEDs) are highly efficient light sources. Depending on the quality and design, LED luminous efficacies can range from 50 to over 200 lm/W, and they are known for their longevity and energy-saving benefits.
• Sunlight: Natural sunlight has a luminous efficacy of approximately 93 lm/W under standard conditions. However, this value can vary depending on factors like atmospheric conditions and time of day.

Luminous efficacy is an important factor to consider when choosing lighting solutions, as it directly affects energy consumption and lighting quality. Higher luminous efficacy means that you can achieve the same level of illumination with less energy or achieve higher illumination levels while using the same amount of energy, which contributes to energy savings and sustainability.