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How many grad students does it take to change a lightbulb?
October 25, 2011 5:01 AM   Subscribe

School me on light bulbs! My lamp and overhead light bulbs just died, and I'd like to use the opportunity to rethink the type I'm using. I'm totally ignorant in this area, so I'll give as many details as possible, inside the fold....

I'm in the UK, if it matters. My lamp bulb is currently a Crompton 60W Triple Life Plus (can't find it in stock online, so no link). My current overhead bulb is currently a Philips Ambiance 20W, which seems to have a color temperature of 2700 Kelvin. I'm not sure whether this is a halogen bulb, but apparently halogen bulbs are Very Bad, and we're meant to be switching to energy saving bulbs (I believe these are equivalent to Compact Fluorescent Lights [CFLs])? I found some bulbs of this type that look good, and was perfectly prepared to buy them, and then I read some disturbing things about their carcinogenic potential. I then looked into LED bulbs, which look awesome in that they seem to use even less energy, but I can't seem to find ones that produce very much light.

Basically, I'm hoping that someone can explain the various types of bulbs and their pros and cons, as well as whether they can be installed interchangeably in my various lamps and overhead lights. If an LED or CFL light says, for instance, that it is 30W but produces 110W worth of light, I can put it in a lamp that advises not to use a bulb more than 100W? Is there any advantage to buying a special (and expensive) "daylight lamp", versus simply buying a daylight bulb for my existing bog-standard lamp? What's the difference between watts and lumens?

Special snowflake details: I have SAD and live in England where the days are often gray, so I'm looking to have my room as bright as possible, and I much favor things that mimic natural daylight rather than something too orangey. I'd also prefer to avoid cancer as much as possible, especially from my light bulbs. I read in my room for 10+ hours a day. At home I have a lamp that seems exactly like this one, and I LOVE it. According to the website, it's a CFL bulb of 27w that feels like 150 watts. I like the clear, intense, steady light it provides. This makes me worry that LED bulbs won't be bright enough. I have a large room currently illuminated with two overhead lights hanging from the ceiling, with shades, as well as a lamp on my bedside table. I believe all of my light fixtures use bayonet bulbs that are standard sized. I'd be prepared to buy more lamps if the consensus were that I should get lower wattage and more lamps. I don't pay for electricity (included in my rent), so a dramatic savings in electricity bills isn't on my priority list, although I like to help the planet as much as the next liberal. In short, I'm totally confused about what my options are. I see a couple of old Ask MeFi questions, but am hoping the products have improved in the past several years. Help me before I blow a fuse!
posted by UniversityNomad to Home & Garden (10 answers total) 5 users marked this as a favorite
 
If an LED or CFL light says, for instance, that it is 30W but produces 110W worth of light, I can put it in a lamp that advises not to use a bulb more than 100W?

Saying "it produces 110W worth of light" doesn't really mean anything. What it means on the packaging is that the bulb is a 30W low-energy (or LED or CFL or whatever) bulb, but it produces the same amount of light as a 110W "regular" incandescant bulb. So yes, you can use it in a "max 100W" lamp because it's only a 30W bulb.

In simple terms, the two bulbs both produce 30W of light, it's just that the incandescant one also produces 80W of heat because its design is very inefficient. (Actually the low-energy bulb will also produce some waste heat, but far far less than the incandescant).

What's the difference between watts and lumens?

Watts is a measure of energy, i.e. how much electricity a bulb uses. Lumens is a measure of amount of visible light, i.e. how much light the bulb gives out. The fact that incandescant bulbs give out so much heat is why they can be of similar lumens, but widely varying watts.
posted by EndsOfInvention at 5:14 AM on October 25, 2011


That article on fluorescent lights causing cancer sounds like complete rubbish to me. Do a search for "Peter Braun Alab" and you find zero hits apart from that Telegraph article, or other blogs that quote it. Not a single primary source to be found anywhere.
posted by pharm at 5:44 AM on October 25, 2011 [2 favorites]


Don't know whether Home Depot is in the UK, but you're going to find most of your questions answered at their lightbulb basics page here. (Click on the various tabs across the top, there's a video on color temp and an FAQ; see also the "New Technology" tab for LED info and CFL basics. See also Wikipedia on color temps.

If you want a lot of light cheap, your best bet today is still to go with CFLs. They're going to fit in any screw-in fixture and as you've found, they can get pretty bright. Ignore the cancer warning crap, just be sure to recycle them properly when and if they ever burn out. If you feel like experimenting, though, you can get some pretty bright LEDs with decent color temps — here's one that's 125W equivalent with a 3000K temp. (That's right in the middle of the typical incandescent range of 3700-3300. However — the look and feel of LED light can also be affected by its color spectrum, which may have spikes in the blue range but wash out reds.)

In situations where brightness is not as important, I think it is starting to make economic sense to switch to LEDs. They're still pretty expensive, and are not yet getting utility company subsidies (stateside), but they will last about 5 times longer than the equivalent CFL while using the same energy or even less. So over the life of the bulb (which might be longer than your own), you'll save relative to both CFLs and incandescents, without the mercury pollution/disposal issues. I've got CFLs throughout my house, but my plan is to start to replace them with LEDs as they burn out. You do need to be careful with color temp on LEDs — a commercially acceptable white LED has been elusive, but they're getting there. Actually they're closer to sunlight than incandescents, which are typically on the yellowish side, but that's what we've been conditioned to accept as "natural" or "warm."
posted by beagle at 6:05 AM on October 25, 2011 [1 favorite]


There's a lot of senseless marketing-speak that confuses these issues.

As EOI explained above, watts are a measure of energy consumption, not light output, so statements like "is 30W but produces 110W worth of light" make absolutely no literal sense. What that means is, "this special bulb uses 30W of electricity, but produces as much light as the terribly wasteful, not-special 110W bulbs you probably grew up with."

"Daylight" bulbs are labeled as such based primarily on their color. Except at sunrise and sunset, daylight tends towards the blueish end of the visible spectrum. So, daylight bulbs are cooler-colored than others. How this is achieved depends on the type of bulb. With incandescent bulbs (bulbs which use a glowing filament, including halogen and xenon), the bluish color is achieved by using bluish glass around the bulb. This produces a nice color effect, but that blue filter just converts some of the red/orange/yellow light into heat. This means that daylight incandescent bulbs are inherently less efficient than otherwise identical incandescent bulbs. With fluorescent bulbs, however, the daylight effect is achieved by using a different mix of phosphors (the glowing coating on the inside surface of the tube). There are no filters turning parts of the light into heat, so there's no inherent inefficiency in daylight fluorescents.

There's a secondary characteristic implied by "daylight" when you're dealing with fluorescents that is irrelevant if you're talking about incandescents. Incandescent bulbs produce light at many wavelengths / colors, and this makes it easy to tell one color from another when looking at objects illuminated by an incandescent bulb. This ease of distinguishing one color from another is quantified on a scale called the "CRI" or Color Resolution Index. CRI is a scale of 1-100, with 100 being equivalent to sunlight. Incandescent bulbs pretty much all have CRIs at or near 100, meaning they allow you to distinguish colors from one another about as well as you can in daylight. At this point in time the vast majority of available/affordable fluorescents and LEDs are both considerably worse in terms of CRI -- especially the LEDs. Older / cheaper fluorescents have especially low CRIs because they use simpler mixtures of phosphors that tend to generate most of their light in a very narrow range of wavelenghts. "Daylight" or "Full Spectrum" fluorecents use a more sophisticated mixture of phosphors to produce light at a wider variety of wavelengths, which in turn improves their CRIs.

I haven't kept current over the last couple of years so my info is a bit out of date, but I believe that LED's really aren't yet substantially better than fluorescents for purposes of general illumination. Taking price into account, they're often worse. Cheap, widely available LEDs don't produce much light per LED, so they use a bunch of them clustered together and get a lighting effect similar to that of older fluorescents, with similarly crappy CRI and similar energy consumption per amount of light produced. Rarer, brighter LEDs have some great advantages over either fluorecents or incandescents in certain special applications (they make great bicycle headlights) but these are still quite expensive.

FWIW, halogen and xenon bulbs are "bad" in the sense that they produce a lot of heat than LEDs or fluorescents, but they're quite a bit better (i.e more efficient) than the really cheap, older-fashioned incandescent light bulbs we all grew up with. Also, if you live in a cool place and heat your place anyhow, the extra heat from incandescent bulbs isn't really wasted.
posted by jon1270 at 6:10 AM on October 25, 2011 [3 favorites]


halogen and xenon bulbs are "bad" in the sense that they produce a lot of more heat than LEDs or fluorescents
posted by jon1270 at 6:14 AM on October 25, 2011


As jon1270 says, color temperature and CRI are the two considerations to look at for compact fluorescent bulbs. I've had good luck with TCP (Technical Consumer Products) full-spectrum bulbs in the past. We've got a couple of rooms where we replaced the 60W incandescent floods in recessed overhead fixtures with 23W full-spectrum CFLs (supposedly 100W equivalent, with a 92 CRI) from TCP and the effect is dramatic. If you suffer from SAD, it can make a huge difference.

A couple of things to keep in mind when picking CFL replacements for incandescent bulbs:

1) The "equivalent wattage", at least in the US, tends to be a bit optimistic. The packaging usually claims about a 4:1 ratio (i.e., "60W equivalent" for a 13W CFL), but I've found if you go by those numbers then the light output will be a little disappointing. Better to jump up to the next notch (e.g., 16W instead of 13W) to be sure you're getting at least as much light as the incandescent you're replacing. Of course, if you're putting it in a fixture rated for 65W, you can get a lot more light (e.g., 23-26W CFL) without worrying about reaching the fixture's limits.

2) Size is a bit more of a consideration, at least with high-power CFLs. The way you make a CFL brighter is to make the tube longer (i.e., more surface area outputting light). That means that both the length and width of the bulb get steadily larger as you increase the power -- if you want to put a significantly brighter bulb in a small/enclosed fixture, then it's worth double-checking the size of the bulb to make sure it will fit before you buy.
posted by McCoy Pauley at 7:04 AM on October 25, 2011 [1 favorite]


I too live in grey England (although in London which has surprisingly low rainfall). About two years ago I replaced all the halogen lamps in our kitchen and bathroom with LEDs which consume comparitively tiny amounts of electricity. I'm pretty pleased with the result - and unlike many other bulbs, they're cool enough to touch and don't make me immediately think of house fires. I gather you can get them in various colour temperatures, including those that mimic daylight. The individual bulbs are somewhat pricey, but they last a long, long time.
posted by rhymer at 7:46 AM on October 25, 2011


People are steering you right in regard to CFLs and LEDs, so I'll just move on to your daylight questions.
That particular daylight lamp you linked is charging for its ultra-modern design not for its light. You can just get a full-spectrum fluorescent bulb and use with whatever fixture you've got already. Full medical brightness is uncomfortably bright. Imagine being outside on a summer day, opening a book and getting such a faceful of light that you have to blink and let your eyes adjust a bit before you can even try reading the text. That's what you're trying to emulate. FYI, one substitute for having lots of light at the source is having the source right up close to you. If the light's half a meter away from you it will be 4 times as bright as if it's 1m away.
The "daylight therapy lamp" type products in general use not only full-spectrum lighting, but also lots and lots of it, usually positioned right in front of you on a table or otherwise pretty close by, to have the light make a difference in your grey winter moods, so with the big panels you're paying for (a) multiple bulbs, (b) moderately heavy-duty electronics, (c) good design to make this medical device somewhat appealing moving from tabletop to wall-mount in your home, and (d) a veneer of medical science, snake oil, and advertizing, as well as (e) full spectrum light, and lots of it. To get (e), you need (a) and that suggests (b), but this can be done without (c) and (d) if you want.
posted by aimedwander at 10:26 AM on October 25, 2011 [1 favorite]


You could make a start by replacing the lamp bulb with a 20 w. daylight bulb. If you like this move on to replacing the overhead bulb with a 30 w. daylight.
I used to be crippled with SAD in the late winter. Haven't looked back since fitting full daylights in place of incandescents.
Harsh and uncomfortable for the first few days you quickly get used to them.
As to pricing the cheapest reliable brand seems to be Prolite. I am a satisfied customer of the cheapest supplier craftlamps.co.uk
posted by Dr.Pill at 11:27 AM on October 25, 2011


Thank you everyone; I'm continually pleasantly shocked by how much MeFites know about far-flung questions, about which I know nothing! All these answers were exceptionally helpful in illuminating (err...) the answers to my various questions, so I marked them all as "best answer". I don't know if that's kosher, but they were all extremely helpful. In the end, I decided to go with daylight CFL bulbs that are energy-saving and 25w (but apparently produce as much light as one of the old 100w incandescent). I'm going to replace my overhead bulbs with those, and if I like them, I'll buy something similar for my lamp. The fact that I now understand the differences between all this stuff is testament to how helpful you all have been. Thank you for such informative, clear, and useful answers!
posted by UniversityNomad at 4:05 PM on October 26, 2011


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