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What is a Lumen, Anyways?

Light bulb technology progression

For many of us, LED lights are a newer technology that can be somewhat confusing. Many of us grew up being familiar with incandescent lights and then CFLs (compact fluorescents) became popular around twenty years ago with an easy to understand conversion (15W CFL = 60W incandescent). LED lights, though, are not as simple.

Incandescent bulbs have gone the way of the dinosaur and are not readily available. Both incandescent and fluorescent bulbs use more energy to run and must be replaced frequently. Replacing more frequently increases the need for more resources – both energy and materials. A common myth is that incandescent bulbs were banned but the reality is that the Department of Energy has increased the minimum efficiency requirements and the older technologies could not keep up with these new energy efficiency standards.

LED lights have been around for more than 50 years but in the past 10 to 15 years have increased in popularity mainly because of the low energy consumption and long life of the of the bulbs. Originally, LEDs were only used in a few select applications such as exit lights and only came in red. Today’s LED technology does a much better job of getting the light from the source to the area.

So how do we know what LED to choose?

A lumen is the light output from a source and remains constant no matter how near or far from the light source. LEDs which produce light from diodes in a bulb or on a fixture (think little light dots) which gives them their name – light emitting diode. These small light dots allow the light output (lumen) to be focused in a specific direction. LEDs still consume electricity (think Watts), but considerably less than their predecessors.

Their ratio (lumens per Watt) helps you understand their effectiveness (think about the concept of miles per hour). The higher lumens per Watt, the higher the efficiency; most LED products either are higher than or are approaching 100 lumens per Watt. All LEDs have a different lumens per Watt efficacy scale depending on their intended use but we’ll save that for another discussion.

Light bulbs today come with a label that is similar to the nutrition label on food to help give a reference that is understandable. Here’s the measurements of your light bulb:

Brightness (lumen) is the lumen output. Feit Electric gives a simple conversion chart:
40 W bulb: look for at least 450 lumens
60W bulb: look for at least 800 lumens
75W bulb: look for at least 1,100 lumens
100W bulb: look for at least 1,600 lumens
Energy Cost and Life of bulb are the next two items on the label. The estimated yearly energy cost is based on a stated $/kWh from the electric utility than what is on the label). The rating of expectations for life is based on laboratory testing (i.e., 3 hours of daily use correlates to 22.8 years of life) and real-life applications may dictate more or less hours of use. Look for the ENERGY STAR® label or DLC label to ensure efficiency and performance.
Light Appearance refers to the color correlated temperature, or the color of light that your eye perceives (measured in Kelvin (K)).
  • 3000K or less – warm
  • 4000K or more – cool
  • 5500K – is the perceived color of sunlight
  • Some lights used in commercial settings are 3500K because it is a good middle ground
Blue light/cool light may not be optimal in spaces for relaxation and sleep.
Energy Used (Watt) is the power required to turn the bulb on. This can help you understand your lumens per Watt ratio ().
 

Low energy use and long life of a bulb are the main benefits people think of when using LED lights but there are many more reasons to make the switch

  • New LED streetlights give crisp clean light on streets. They also have the ability to direct the light eliminating most of the skyglow and light trespass, both forms of light pollution. The old sodium-based lights give off a yellow “glow” which dims quickly and floods the area with light.
  • The ability to choose either cool or warm light depending on your needs. A color-tunable light (some can work with your smartphone) can be multiple colors.
  • LEDs can be turned on and off more frequently without impact on life of bulb.

Even so, there are times when it may not make sense to use LED lights.

  • LEDs are good at cooler temperature applications, however, prolonged exposure to higher temperatures or being installed in fixtures with a sealed enclosure (some outside fixtures) can cause quicker failure of the light.
  • Another area of concern is lighting circuits with a dimmer switch so you must consult an electrical professional to ensure it’s capable of being upgraded to LED.

Don’t despair – because the LED technology is so widely used today, there are LED fixture designs for almost any application.

One last reminder when upgrading to LED lights:

  • Make sure globes and shades are on a regular cleaning schedule. We recently took the globe off the ceiling light by the stove and cleaned it. We were amazed at how much brighter the kitchen was with just a simple cleaning. Dust the bulbs themselves (while off) as the dust build up over time diminishes the light output.

Now hopefully you can understand why LEDs required a new way of labeling and a new way of thinking about lights.