LED Lamp Efficiency ? The Great lm/W Fraud

Lumens per watt is a key metric for assessing the efficiency of a light fitting, indicating the amount of light produced per unit of power consumed. It’s beneficial for the environment, your budget, and your vision.

Key Definitions:

Lumens: The total light emitted by a source (output).
Watts: The electrical power consumed by a source (input).

Efficiency Question: “How much light (lumens) do you get for each watt of power?” The answer: more lumens per watt the better!

Misuse of Metrics: Simple metrics like lumens per watt are often misused. As technology advances, what was considered efficient years ago may now be outdated. For instance, an LED tube delivering 100 lumens per watt was good in 2020s, but now 130 lumens per watt is the standard.

Beware of Overstatements: Some manufacturers claim extraordinary efficiencies, such as 175 or 210 lumens per watt, which can be misleading. The maximum theoretical efficiency for white light is about 250-350 lumens per watt, but most practical applications fall short of this.

Understanding Lumens per Watt:

Naked LEDs: Lumens per watt figures are often quoted for naked LEDs without drivers, reflectors, lenses, or diffusers. These figures can exceed 250 lumens per watt in lab conditions but are not reflective of real-world performance.

Light Fittings: The actual performance of a light fitting (luminaire lumens per circuit watt) considers all components, including drivers and diffusers, which consume power and reduce light output.

Cold Lumens vs. Luminaire Lumens:

Cold Lumens: Measured in ideal lab conditions, often higher than what you get in real-world usage.

Luminaire Lumens: The actual light output of the complete fitting, considering all losses.

Practical Examples:

A downlight consuming 10W for LEDs and 2W for the driver should be rated as a 12W fitting.

LED per Watt vs L:uminarie Lumens (including Driver) :

Lumens per Watt: Relevant for LEDs in lab conditions and to develop a product but not practical.

Luminaire Lumens per Circuit Watt: The correct measure for comparing light fittings.

Final Thought: When evaluating light fittings, luminaire lumens per circuit watt is useful but not the only factor. The design must ensure proper light distribution and minimal glare for a comfortable living and working environment.