For most people, choosing a lightbulb is an ordinary task. We simply walk into our local hardware or grocery store, find a pack of two or three, and head back home without a second thought. It’s true, however, that each of the bulbs on those long aisle shelves have slight differences that can make major impacts on the lighting of your home and the look of your lamps and lamp shades. Here are the four key things you need to think about when buying a lightbulb.
For years, when we were concerned with the brightness of a bulb, we thought in terms of wattage (more on this in a bit). Seeing “40W” or “100W” printed on the top of those old incandescent bulbs told us everything we thought we needed to know about whether we would be able to read the print of a magazine or thread a needle in our living rooms. And yet, bulbs with the exact same wattage can produce different levels of brightness. This is even more true now than it was 20 years ago.
Be it an incandescent, compact florescent (CFL), or LED bulb, brightness is best measured and described in lumens. The word “lumens” is defined as:
A unit of luminous flux in the International System of Units, that is equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.
Whether or not that tech-speak is helpful to anyone, this should be: The higher the lumens, the brighter the bulb. For instance, that traditional incandescent 100W bulb from the 80s? It gave off, on average, about 1600 lumens. So when you look on a package of CFL or LED bulbs that says “100W Replacement,” what they’re really telling you is that the bulb in the box emits around 1600 lumens; just the right amount for many of your household’s lamps
So if wattage doesn’t dictate the brightness of a bulb, what is it? Simply stated, the wattage of a bulb tells you about the amount of electricity that the bulb needs to operate, and most importantly, its impact on your electric bill.
Take that “100W Replacement” LED bulb we discussed earlier. While that light will give off roughly 1600 lumens, the same as the older and now defunct 100W incandescent, it will require only around 15W of electricity to power the light. That is an 85% reduction in electricity use, meaning that the LED bulb is going to cost you far less to operate each time you flip that switch.
While LED bulbs deliver, on average, an 80-85% decrease in energy consumption, CFL bulbs deliver around 70-75% savings when compared to incandescent. Paying attention to the energy needs of a particular bulb can save you a lot of money in the long run, and who doesn’t want that?
3. Color Temperature
Perhaps the most overlooked and misunderstood aspect of in-home lighting is color temperature. Have you ever noticed that some bulbs give off a soft, almost yellow light, while others are much whiter, often even bordering on blue? This all comes down to color temperature, and it can drastically affect the look of your lamp, lampshade or living space.
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. Most bulbs you will purchase for your home will fit into one of three categories: Soft or Warm White (2000K-3000K), Cool White (3100K-4500K), or Daylight (5000K-6500K).
One of the biggest mistakes you will see in home lighting is the placement of two drastically different color temperature bulbs in the same living area. Often you will see this in fluorescent tube fixtures in offices or retail shops where bulbs are replaced with what is cheapest or most readily available. This can be distracting or even uncomfortable to the eye.
While certain living spaces such as bedrooms or living rooms often utilize warmer bulbs, other areas such as kitchens or home offices are sometimes lit with a cooler temperature between 3000K and 5000K. It is important to consider, however, whether the lighting in the two rooms overlaps, particularly in open concept designs.
Don’t forget that the bright white shade you bought and love so much will only be as white as the bulb behind it. Warmer bulbs will give a softer, more yellow look to your shade, while only daylight bulbs will keep the fabric color true to what is seen when unlit.
So if we know that color temperature is important, then how to we make sure bulbs from different manufacturers or different boxes will live up to the color temperature listed on the packaging?
CRI, or color rendering index, is a measurement of how accurate the color temperature of the bulb will be. Just like the colors on a computer monitor, the color temperature of bulbs can vary slightly between product runs or manufacturers. In creative realms such as video production or photography, color temperature matching is vital, and this is where the focus on CRI began.
Nowadays, light bulb manufacturers are seeking to bring that same level of confidence into your home, utilizing a CRI scale of 1-100 to give you confidence in the color temperature of your bulb. Most LED bulbs these days have CRI scores in the 70s or 80s, while some higher-end brands have CRI levels in the 90s. Sometimes a higher CRI score can impact the brightness (lumens, remember?) of the bulb, so be sure to pay attention to both.
So next time you go to pick out your next batch of light bulbs, be sure to consider the four keys to buying a light bulb: Lumens, watts, color temperature, and CRI. It could make your home even more beautiful than before, and could save you some money in the long run, too.