I’m as much of a fan of saving money as the next guy… so when it came to energy-saving light bulbs, I was excited. Who wouldn’t want to shave a few bucks off their electric bill every month? Unfortunately, I hated the nasty blue glow of compact-fluorescent bulbs. Any time I see one of those, I feel like I’m in a hospital or an office. It doesn’t have the warm, inviting light I associate with a household light. So, what was I to do?
See that bulb on the left? It looks like stress and agony.
(Image credit: Ramjar on English Wikipedia.)
Well, it turns out, they’ve been working on the whole “ugly blue color” thing! The “color” of light is actually referred to as “color temperature” and it’s on a scale expressed in Kelvin. If you see a figure like “3500K” on a light bulb package, that’s your color temperature! This color temperature scale varies from “warm” (reddish) to “cool” (bluish). So, if you want your bulb to look a certain way, you just have to find a bulb with the right color temperature! Thankfully, the options have been increasing exponentially lately.
So, what color temperature should you be looking for? If you want a bulb that looks like a real, old-fashioned incandescent lightbulb, you want something that’s about 3000K. This color temperature is also referred to as “soft white,” which makes normal-looking bulbs really easy to spot.
If you really like the bluish color (I don’t know, maybe you’re a masochist…), you’ll be looking for a higher value on the Kelvin scale. Something like 5500K should do the job. And if you want something really red looking, you’ll want to go well below 3000K.
After doing some shopping around, I settled on soft white LED bulbs from Cree, a company based in Durham, NC. These have several advantages. The 60 watt replacement bulbs use only 10 watts of power, meaning they use 1/6th of the power of a regular light bulb! And, since the bulbs are LED-based, they will never burn out, unlike traditional or compact-fluorescent bulbs. Most importantly, they’re pretty cheap for LED bulbs! Where I live, Duke Energy (the local power company) subsidizes the bulbs, so I can purchase them at $5 a pop – or about $18 for a 4-pack.
True to their “soft white” name, the Cree bulbs produce a light that is indistinguishable from a traditional incandescent bulb. I’ve replaced every regularly-sized light bulb in my house with them, and you’d never guess I was using LED bulbs. And, at current electricity prices, they pay for themselves really quickly!
[Related Nerdy Questions…]
- How do you know they pay for themselves? Well, at current electricity prices around me, it costs roughly $1 (more like $.94) to run something that pulls 1 watt of electricity for a year. That makes back-of-the-envelope calculations really easy. The LED bulbs use 50 watts less electricity than the incandescent bulbs they replace. That’d be a $50 savings every year if the bulbs were on continuously. So, even if I only have them on 10% of the time, I’ll get my $5 back in a year. Even if I only use them rarely, they’ll still pay for themselves in a few years… And remember, they’re LED, so they never burn out! So, eventually, I’ll also reap the cost benefits of not having to replace bulbs all the time…
- Isn’t Kelvin a measure of temperature, just like Fahrenheit and Celsius? What does it have to do with red and blue light? According to Wikipedia, we use Kelvin as a scale because “a black body radiator emits light of which the colour depends on the temperature of the radiator. Black bodies with temperatures below about 4000 K appear reddish whereas those above about 7500 K appear bluish.” What’s a black body radiator, you ask? I’ll let you do your own research on that one – it’s fairly interesting reading. Suffice it to say that it’s a theoretical object used in physics.
- Why’s the scale backwards? Shouldn’t higher temperatures be “warmer,” not “cooler”? See the question above… A “black body radiator” that is literally “hotter” (in regular temperature terms) emits bluer or “cooler” light. So the scale gets switched. Now you know!
- Does this have anything to do with the changing colors of the sun or sky? Nope! Rayleigh scattering is responsible for that… If you’re interested, I’ve written about that previously…