When we only had incandescent bulbs available for most of our household lighting, we were familiar with a warm look to our lighting. When CFLs came along, we started seeing lights that appear more white and sometimes almost blue when compared to the warmth (think "yellow") of incandescent bulbs. These whiter or bluer colors are considered "cooler" in appearance.
The warmth or coolness of light is known as its color temperature. This has nothing to do with actual heat from a light bulb, but only with the appearance of the light. Besides using terms like "warm white," "cool white," and "daylight" to describe these color temperatures, we also rate these in kelvin, which is a temperature scale.
It's important to note that there is no absolute consensus on what kelvin ratings equate to what color temperature descriptions. Visit different websites and you'll get different answers. But the following is a good general guideline to what these descriptions mean. (Also see the image at the end of this post.)
A "warm white" bulb is usually considered to be below 3000K (3000 kelvin). This is the light color provided by an incandescent bulb (2700K) or halogen bulb (2850K). As an incandescent or halogen bulb is dimmed, it becomes even warmer -- slightly orange -- in appearance. It may dip to about 2200K or below. The lower the kelvin, the warmer a bulb appears.
CFLs and LEDs can also provide a "warm white" appearance, and you'll need to choose CFLs or LEDs if you want the other color temperatures listed below.
Bulbs that provide light at around 3000K to 3500K may be considered "white" or "soft white."
Bulbs that provide light at around 4100K to 5000K are considered "cool white" and these start to have a slightly blue feel to them.
Bulbs that provide light at around 6500K are considered "daylight bulbs" and these have a definite blue and cool sensation to them.
Take a look at the image below and you'll get an idea of how different lighting can affect an office setting. Choosing between these types of light bulbs is a personal decision. In a household setting, you may like one color temperature and stick with that throughout the home; or you may choose different color temperatures to set a different feel for each room. For instance, you may want warm bulbs in dining rooms and bedrooms, white bulbs in kitchens, and cool bulbs in utility areas like laundry rooms and workshops. Again, it's a matter of personal taste.
When you shop for light bulbs at Lighting Supply, you'll find a refinement option on our site to sort bulbs according to their color temperature to help you more easily find the bulbs you need.
And this is why lighting professionals exist.
Unless you work in road lighting, would you think about the fact that these lights accumulate dirt over time, decreasing the amount of light that reaches the roadway? And if you would have thought of that, would you have remembered that LED street lights might collect more dirt?
Why would these accumulate more dirt? Because LED lamps last longer than the HID lamps that were used for years to light our roads. So a study looked into this topic and concluded that ... this is a hard thing to study. LED road lights come in many forms, and it's hard to test all brands and all forms. But due to the long lives of LEDs, "luminaire dirt depreciation" (LDD) needs to be factored into lighting plans.
At the very least, planners should think through how the roads will look by end of lamp life with LLD taken into consideration. In a better scenario, operators will plan on cleaning the lights and recapturing the available light, minimizing the impact of LDD. Read more about it on the IES website.
In late 2017, we saw a study from the University of Michigan that talked about the best approach to saving energy with light bulbs. In short, it suggested replacing all incandescent and halogen bulbs with CFLs (compact fluorescent lights) or LEDs, but not necessarily replacing CFLs with LEDs yet.
The reason? CFLs are already highly efficient compared to incandescent and halogen bulbs, while you don't step up efficiency nearly as much when replacing CFLs with LEDs. The study points out that LEDs may continue coming down in price and are likely to get even more efficient, so waiting another couple years (or until a CFL goes out) is a good idea for CFL replacement.
The study also points to ideas like replacing more frequently used bulbs first and considering the most efficient bulbs (LEDs) sooner in places like California, Hawaii, and Washington, DC, where electricity costs are high. We think all of this is accurate when your only concern is electricity use and saving money.
But there are other reasons to consider replacing CFLs with LED bulbs right now:
That said, we should point out that not all LED bulbs are created equal. Some brands provide a high-quality lighting experience while others -- usually inexpensive bulbs with unfamiliar brands -- could fizzle, dim, render colors poorly, etc. We encourage sticking from known brands who have reputations to maintain. Also consider looking for 25,000 hour ratings on LED bulbs -- shorter ratings usually come from low-quality components.
In any case, if you do replace CFLs, don't forget to take the CFLs to an appropriate recycling center. Because they contain a small amount of mercury, they should never be thrown in the trash.