When choosing a lighting setup, what is advertised on the box does not always translate to the real-world performance. This is especially true for nominal lumens, which often overestimate a luminaire’s (lighting fixture) brightness over time. Effective residual lumens offer a more accurate picture, says Andrea Barausse from IESSA.
LED luminaires are expected to maintain brightness throughout their lifespan, which is considerably longer than traditional light fittings. However, factors such as lumen depreciation (gradual light loss) and ambient temperature can significantly impact this. Understanding how these factors interact, known as ‘lumen and temperature behaviour’, is crucial for choosing long-lasting, high-performing luminaires.
While lumen per watt (lm/W) is a common efficiency metric, focusing solely on this data can be misleading. To ensure a lighting system meets required standards (Lux levels, OSHA, SABS, etc) and that it maintains performance, lighting specialists need to consider a broader range of light characteristics.
For example, delivering a good return on investment (ROI) for clients means ensuring the promised performance aligns with reality. This requires understanding how lumen depreciation and temperature affect a luminaire, then selecting products that meet the project’s specific needs.
Manufacturers rate LED products based on their ability to retain a certain percentage of initial lumens over time. These ratings can vary significantly, though. To set accurate expectations, it is vital to consult the manufacturer’s data sheets on lumen maintenance under specific operating temperatures.
In essence, effective residual lumens are about understanding how lighting performs over any given period, particularly in varying temperatures. By considering both lumen depreciation and temperature behaviour, lighting professionals can make informed decisions that lead to better lighting outcomes and a maximised return on investment. If you are being sold a lighting solution based on price alone and these points are not being addressed as you make your decision, you should be wary. Chances are that great price point is likely going to come back to haunt you when your illumination solution does not light your world as you had hoped.