Should I buy LED or CFL light bulbs?
mnn.com
mnn.com
They have warnings along the lines of that damp environments like bathrooms, and turning them off quickly (less than 20-30 minutes on) significantly decreases the life of the bulb.
So if you plan to use CFLs that will be turned on and off quickly like bedrooms, bathrooms, hall lights, etc - basically everywhere except the living room / reading light that you plan to have on for hours at a time - CFLs will die faster than an incandescent - within 12-18 months of light use. You basically get punished for being good at turning off lights when not in use.
If I'm not mistaken, LEDs being solid state don't lose efficiency over time like that, so it's always working at peak output as long as the driver lasts. That alone should make it more cost effective.
You are mistaken, LEDs most definitely do lose efficiency.
http://web.archive.org/web/20090410145015/http://www1.eere.e...
LEDs and CFLs are about the same as far as losing efficiency.
I'm not aware of the design of these LED bulbs you mention, but they might work under the same principles, the LED just replaces the mercury as the UV source.
Since it is solid-state, though, the LED is expected to continue operating long after it reaches 70% brightness. 70% is simply the assumed reference point at which the consumer becomes annoyed and decides to replace the LED.
Source: Department of Energy, "Lifetime of White LEDs", http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl...
> the Alliance for Solid State Illumination Systems and Technologies (ASSIST), a group led by the Lighting Research Center (LRC), recommends defining useful life as the point at which light output has declined to 70% of initial lumens (abbreviated as L70) for general lighting and 50% (L50) for LEDs used for decorative purposes.
As stated in the DOE that I linked to: "The primary cause of LED lumen depreciation is heat generated at the LED junction." Because it's the primary cause, you can't just ignore it and say that LEDs barely degrade in the absence of heat. You have to consider the heat when calculating LED lifetime.
The stated lifetime on the LED packaging makes a number of assumptions, one of which is that the LED is run at room temperature.
In climates like the northeast U.S., the heat that incandescent bulbs generate isn't wasted for most of the year: it helps heat your house, which means you burn slightly less oil or gas in your furnace. They're only wasteful during the summer months. And a CFL probably takes more energy to manufacture and recycle, and needs more packaging material to prevent breakage, since nobody likes to clean up toxic mercury spills. (After having read the dire warnings on the EPA's web site about what procedure to follow if you break a CFL, I never wanted buy another CFL again.)
In very, very cold areas, the COP of the heat pump will reduce to 1, and in those cases the incandescent bulb isn't wasting any energy.
Also, if you're concerned about CFL taking more energy to manufacture and recycle, also consider the fact that a typical CFL lasts the lifetime of multiple incandescent bulbs.
(Note: I'm not trying to make any particular point other than the only valid way to compare two technogies is with a proper cradle to grave analysis)
[1] http://www.nrdc.org/legislation/files/lightbulbmercury.pdf
If electricity was cheaper than oil/gas, then you wouldn't use an oil/gas furnace to begin with.
So, an efficient lighting system is saving you money.
At this point I find that the LEDs are cheap enough to be worth buying, one to avoid the pain point of CFLs (slow start, fragile, early death), and two to support the industry into the next generation.
The DOE knows they didn't do so hot with CFLs and anybody you talk to will complain about them. They are not making the same mistake twice, and reports like this, as well and monitoring programs like CALIPER (http://www1.eere.energy.gov/buildings/ssl/caliper.html) provide great independent data for consumers to read if they want real numbers.
You have to realize that any CFL plant is just being run out to try and squeeze every last cent from the facility before it gets shut down, so the quality is going to drop as companies lose interest in them. If you buy from a reputable company (Philips, Cree, GE, etc.. etc..) you'll do much better than these averages.
(I used to be in the lighting industry)
Are you sure you're not looking at SPDs for CFLs instead?
LED lightbulbs at least typically seem to have relatively broad and even spectral coverage, even if the distribution is a little lumpy and only a rough approximation of a BB.
All the SPDs of CFLs I've seen on other other hand, are vastly worse, with lots of super intense and narrow spikes in the middle of large areas of almost nothing.
In other words, CFL SPDs look nothing like a BB SPD, whereas LEDs can kinda-sorta-come-close-if-you-squint (it depends on the particular bulb, but some are not bad at all).
[LED lighting also seems much more likely to improve significantly in the future, as it's been developed for a much shorter time than florescent lighting.]
I'm not running a lab or anything where CRI is critical. I had simply preferred high-CRI when I was given the luxury of opting for that when I switched my house from incandescent to fluorescent ten years ago. I would like to see better CRI in LED, but to-date it doesn't seem to be a focus, even amount the high-end brands.
Also, it seems like we are reaching diminishing returns outside of potential manufacturing efficiencies at some point in the future. How far can we go to make lighting efficient until it makes more sense to focus on other areas of energy consumption like the systems that manage your lighting or other home/office utility infrastructure like the Nest thermostat?
There are many things to take into account when purchasing bulbs; chance are, the time it takes to change them is not one.
The absolute theoretical max for efficiency is 251 lumens/watt. I find it incredibly unlikely that they are going to reach 200 with white light.
What I think will happen is they'll get there by having a very low CRI, with off-color light. It's already happening in the market - all the high efficiency bulbs have a CRI of 80 (the minimum needed to get an Energy Star rating). But the CFLs they are compared against often have a CRI of 90.
Quote from that: "[...] this new LED model achieves an impressive 200 lumens/watt while meeting the criteria required for comfortable workplace lighting (ie. a color temperature of 3000–4000 kelvins, a color rendering index of at least 80, and an R9 saturated red level of no less than 20). That's not the same as having a super-efficient LED that produces horrible light quality for the sake of breaking records."
Also: "expected to hit the market in 2015 for office and industry applications".
Where practical, both for heat dissipation and optical purposes, it's far more ideal to use fixtures which are actually designed around these technologies rather than just throwing retrofit bulbs into crappy incandescent fixtures.
I'm really hoping we see more of these sold to the consumer markets. For good quality LED products, you're talking about 50k hour life which makes a non-user-replaceable solution not seem that bad -- some cheap incandescent bulb sockets might start having trouble after equivalent usage.
On the other hand, I'm concerned that we're going to see a repeat of all the cheap low quality products we've seen in CFL-land.
I recently tackled the challenge of equipping an enclosed light fixture with an LED bulb. I ended up going with the Xledia D series A19 bulb. (Warning, Xledia is a Chinese company and I think they've hired a gray-hat SEO company to spam up Twitter and the like; but don't let that taint whatever merits they have in engineering.)
The D125 [1] is my favorite LED bulb to-date. My wife, an electrical engineer, was incredulous: "you bought a seventeen watt LED bulb??" It's quite astonishing to fire that beast up. 2000 lumens. And true to its spammy marketing ("the most efficient series of omni-directional LED bulbs suitable for fully enclosed fixtures"), its temperature management is impressive.
After hours of operation, its lens is merely warm, heatsink is hot but not flinch-inducing in the same manner a fully-warmed incandescent bulb would be.
[1] http://www.amazon.com/dp/B00EW6R0EC (available elsewhere as well)
covers all the basics - CFL lifespan, lumen depreciation, etc.
As a consumer, I want to know $/lumen. That's it.
The last time I looked, the energy savings for LED were swamped by the upfront purchase costs. CFLs were still significantly cheaper.
Of course, that's for NZ, and the US might be different.
NZ Prices from Consumers NZ (Bulb + Running over 5 years)
Incandescent: $115 CFL: $30 LED: $95 (60W equiv), or $57 (40W equiv)
800-lumen LEDs are already down to $15-20 unsubsidized in the United States. Some utilities also provide a subsidy for each LED.
Granted, the 10-watt LED does not save you much in power costs over the 13-watt CFL of equivalent brightness. However, the LED is already cheap enough to be a viable replacement for incandescents in bathrooms, and other areas where high cycling rates will kill CFLs.
I just looked on the home hardware website, and they don't sell any MR16s that are more than 6.5W. The 12W bulb is a 650 lumen and sells for NZ$13. However, a CFL goes for less than NZ$4. That $9 will buy you a lot of electricity.
At 3hrs/day, and NZ$0.25/kwh, that's a break even point of ~5.5 years... I think... (6W difference in power usage between CFL and LED?)
Going from a 20W halogen to a 10W led would result in a payback period of 3 years. To me, these sorts of things need to pay off in their warranty period. :)
Seeing a close-up of yourself with CFL complexion when you first wake up and brush your teeth, when you get out of the shower, before you leave the house... it subtly takes its toll after a while.
It's not always about efficiency.