FAQ – Lighting

Color Rendering Index (CRI) is a way to measure a light source’s distinctive attributes. It is an assessment of how the light source shows object colors “naturally” when compared to a familiar basis of reference, either incandescent light or daylight.

In the light bulb industry, the Average Rated Life (ARL) is how long it takes for half the light bulbs in a test batch to fail. … Some bulbs may have failed within 50 hours, some within 450 hours, some within 700 hours, etc. but half were dead within 1000 hours.

Color temperature is a way to describe the light appearance provided by a light bulb. It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000. Typically, Kelvin temperatures for commercial and residential lighting applications fall somewhere on a scale from 2000K to 6500K.

Kelvin Color Temperature Scale

If you heat up a metal object, the object appears to glow. Depending on the Kelvin temperature that’s heating the object, the glow will appear in various colors, such as red, yellow, or blue. The Kelvin color temperature scale ranks these colors from warm to cool, or low to high. Using this scale, we can gauge what color of light a bulb produces:

• Less than 2000K: dim light, close to candlelight
• 2000K-3000K: warm light with hints of yellow
• 3100K-4500K: bright white light
• 4600K-6500K: bright blue-white light (daylight = approx. 5200K)
• 6500K and up bright bluish light

A good rule of thumb is the higher the temperature, the “cooler” the color. For example, a 5500K hospital-grade bulb is cooler than a 2700K bulb you’d likely use in your living room.

Most residential lighting applications fall somewhere on the scale between 2000K and 4500K. It’s important to know what light temperature bulbs you have in fixtures around your home. If you ever replace one with a different temperature than its neighboring light sources, you’ll notice they aren’t the same “color.”

If you’re like the majority of businesses that are converting their lighting to LED and your primary goal is energy savings, one key metric to look at is lumens per watt (LPW) – a unit of efficacy. Unlike lighting product specifications, understanding this metric is pretty easy.

Lumens measure how much light you are getting from a bulb. More lumens means it’s a brighter light; fewer lumens means it’s a dimmer light. Lumens are to light what. Pounds are to bananas.

This marking, known as a UL listing, means the product has been tested by Underwriters Laboratories for fire safety and electrical safety. A UL lighting fixture is labeled to indicate the product has passed the specific safety requirements necessary to be used by consumers in their homes and in places of business.