Watts the difference?
The Caribbean is a very specialist market; not all generalised rules apply. Not only do we have to factor in heat, humidity and corrosion, but we also have particular needs regarding durability and logistics.
Over the following four issues of Illuminate, we will discuss the key factors you should consider when selecting lighting and the critical information needed.
Today, we want to talk about the difference between watts and lumens. Traditionally, we were trained to think about watts and wattage. This has changed; it's now all about lumens. The Merriam-Webster dictionary defines lumens as "a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity", which, whilst accurate, doesn't make it easy. In short, watts measure energy; lumens measure brightness.
A watt measures how much electricity the bulb requires per second, whereas a lumen directly measures light output. Lumens indicate the degree of brightness, or the amount of visible light to the human eye, regardless of the bulb type. Like watts, lumens are a standard measurement but are a more accurate indicator of light because it tells you how the bulb actually performs instead of how much energy it consumes. This ensures that whoever is specifying gets the correct lighting levels and also meets legal requirements in instances such as libraries and airports.
It is also important to examine the difference between source and delivered lumens. Source lumens is the amount of lumens that come out of a LED light engine. Delivered lumens is what is actually delivered after it bounces around the reflector and appears, so in spec sheets, you may see:
Source: 100
Delivered: 70.
Manufacturers often offer source lumens data as, understandably, it looks better. Still, as a specifier, it's essential to know the delivered, as delivered lumens are a more reliable indicator than source.
Everyone intrinsically knew that a 100w bulb was brighter than a 40w, but often, not why. A high lumen value does not necessarily equate to high wattage. However, the higher the lumen rating, the brighter the lamp will appear. While the numbers can vary slightly, the chart above shows a comparative measure against incandescent bulbs and that an LED's energy use is substantially smaller.