LED 101: Understanding LED Bulbs and How to Shop for the Right One
Posted by Hagan Schmidt on Nov 9th 2014
As the nation moves away from incandescent lights and towards energy efficient alternatives it has become increasingly important for American consumers to become savvy on lighting terminology and to learn the factors that are important to consider when shopping. The learning curve for LED lighting is a little bit more than many expect; it goes beyond just total lumens, watts, and colors. Huge advancements have been made in the LED lighting industry that has made it so that there are replacements for virtually any traditional bulb, both in the residential and commercial sectors. In this blog we will look at some of the key factors to be aware of when picking out your LED lights, after all, they may be with you for 17 years or more. Color Rendering Index (CRI) LED lights have come a long way and they have some fantastic color rendering abilities. The governing agencies have defined CRI ranges in four categories; low (0-40), medium (41-75), high (76-90), and very high (91-100). Knowing which range of CRI to purchase for your application is very important when choosing LED bulbs. Some LEDs are even able to achieve full spectrum ratings with a Color Rendering Index (CRI) of 95. What this means is that they are able to accurately render all colors without causing color distortion. These bulbs are great for those who need them, but it is important to know when and where to use a very high CRI rating. For example, an art gallery will want a bulb with very high CRI so as not to discolor any of their pieces. In our homes we typically don’t need the highest CRI and usually a bulb with a CRI of 70 to 85 is sufficient. Lumens: Total vs Delivered The lumen output difference between incandescent and LED is often misunderstood, and is very important in understanding the advantages of LED lighting. There are several factors to take into consideration, from the way the bulb is designed, to the fixture that it is being used in. A good example is in kitchens. Many of the light fixtures we choose for lighting kitchens are designed to direct light to various spots such as the counters, stove, and sink. It is important in these settings to use light as efficiently as possible to minimize the amount of power consumed in order to get enough light to these work areas. Incandescent bulbs typically use a series of reflectors inside the bulb or the fixture to direct the light where it needs to be. Each time the light is reflected some of it is lost and at times even wasted. The light actually reaching the work space (delivered lumens) can be as much as 20% to 40% less than the light that is being generated (total lumens). LEDs, on the other hand, are very directional lights and can be manufactured with various beam angles. This high degree of customization in LED bulbs makes it possible to greatly reduce wasted and inefficient lumens allowing the light to reach where it is needed. When the correct bulbs are chosen the loss of light is minimal, under 10%, and in some cases you can even get it down to 0%. Comparing incandescent to LED becomes more important by looking past the total lumens to the delivered lumens. Looking at a 60 watt incandescent that has 800 lumens but generally only deliver 480 lumens. Directly replacing that bulb with LED of the total 800 lumens at least 720 of them are being delivered. We frequently hear that LED bulbs are so much brighter than incandescent; this is typically the reason why. If the amount of light before was the amount you needed then an even lower wattage LED replacement can used to achieve the 480 delivered lumen output. Color Temperature Color temperatures are measured on the Kelvin scale and gauge the warmness or coolness of a light. The easiest way to think about this is to think about a flame. As a flame gets hotter it goes from a reddish hue to a bluish hue. The same goes for lights. Higher Kelvin temperatures give off more blue tinted light and lower Kelvin temperatures give off more red tinted light. The standard incandescent is rated at a warm color temperature around 2700 Kelvin. These are the bulbs commonly used in most homes. Many LEDs are manufactured at 2700 Kelvin to give the same warm soft light as an incandescent. While it is the norm, it is not always the best color temperature. A good example is in your bathroom. Have you ever gotten ready and then gone outside only to discover that you look drastically different than you did inside and no longer like what you see? Many times this has to do with both the CRI and the color temperature of your lights. While no light is truly white, between 4800K and 5200K is close. These are typically called things like Pure White, Daylight White, or Natural White. Combined with a high CRI you will see very similar results in the mirror and out in the sunlight. The learning curve to LEDs goes even further than these topics and there is so much more that could be covered from spectral power distribution to understanding how our eyes even perceive light, but for now you should have a great foundation to start with. When you correctly combine color temperature, CRI, beam angles, lumen output (total and delivered), you will be able to successfully find the right LED for your lighting needs. Traditional forms of lighting overlooked some details that help us determine the right lighting combination at greater energy and overall cost savings over the lifetime of the bulb. After reading this you should have the knowledge you need to get started on making the right choices for your home or commercial lighting needs.