How are your lights powering you? From the very moment we wake up to end-of-day bedtime texts, the light around us has a quiet but notable impact on how we live our lives. Direct light creates stimulation for the senses, which in turn has mental and physiological effects. A number of studies have been conducted on the psychological impact, giving rise to light therapy as a way to treat Seasonal Affective Disorder and depression.

And it’s not just emotional: Indoor light has also been shown to affect school and work performance. A joint paper by the Rocky Mountain Institute and the Department of Energy found that when the Reno retrofitted its Main Post Office with new lighting, productivity improved by 8% and saved them $400,000 in one year alone.

Not all light is created equal. Bulbs shine on a range of color (measured in Kelvins, or K), and it is along this scale that our mind and body are affected. Let’s break down those effects by color temperature:

  • Red or Warm Light (2000K – 3000K) Typically found in incandescent, candle, and colored decorative bulbs.
    Indoor light in the warm end of the spectrum typically shines as a soft orange or yellow. It first and foremost has a calming effect, reducing signs of depression in hamsters when exposed to it nightly in a 2013 study. The shortened wavelength of red light is less disruptive to one’s circadian rhythm (i.e., sleep cycle), making it easier to get a full night’s rest, and therefore better retain memory and increase productivity for the following day. In a human trial, those subjected to periods of red light had higher emotional arousal, turning into a more positive overall mood.
  • Blue or Cool Light (3100K – 4500K) Typically found in fluorescent, tungsten-halogen, and light-emitting diode (LED).
    This light is usually found in basements and bathrooms and are the standard for the average office environment. Providing a brighter and more vibrant ambience, cool blues and whites are the light for improving work performance. A recent call center study demonstrated improvements of 30% or greater in the areas of concentration, light headedness, lethargy and sleepiness among those who worked in high grade fluorescent lighting. For these reasons cool light shouldn’t be used close to bedtime, and it may cause headaches and stress for those with light sensitivity.
  • Natural Daylight (4600K – 6500K)On the color temperature scale, natural light is even further on the “cold” side, but the biggest benefit is the connection to the great outdoors. An office offering daylight and a view, workers are found to work about 12% faster, and perform 25% better on tasks requiring memory recall. Similar effects were seen in school classrooms; students learning in natural light scored 20 to 26% higher on reading and math tests over the course of a school year. Less stress and eyestrain were two big reasons why.

Depending on your own conditions and preferences, you can mix and match the three kinds of light to improve your mood and health—and be more productive in the long run. There are a number of light buying guides online to help guide your decision making, including what is best for each room.

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