EnergyRealist

…Camera, Action…                                                                                                    [Updated Jul 29,2010]

Those are my bathroom lights.  I thought I’d try and see just how these lights compare in real life.  The price at Home Depot (and Lowes, and presumably other big chain stores) has now got to the point where it’s no longer a big deal to buy energy saving light globes.  The question is do they do the job?

From left to right the lights are:

• A CFL (Compact Florescent Light – or Lamp), with 800 lumens of light output, roughly equivalent to an incandescent 60W globe.  It draws 14W of electricity.  It is supposed to last 8000 hours and has a 7 year guarantee.  The light is described as “soft white”.  Price: $8 for 2 – $4 per globe – which is more than the usual CFL, because this one is nicely packaged in a round glass enclosure, so it looks like a more conventional globe.
• A LED (Light Emitting Diode).  429 lumens, equivalent to a 40W incandescent.  It draws 9W, should last 50,000 hours and has a 5 year guarantee.  The light is described as “bright white” and has a 3032ºK corrected color temperature.  Cost at Home Depot around $20.
• Furthest right is an “old” clear glass incandescent globe rated at 60W.  Price: less than a dollar.

The CFL and LED are both made in China – where else?  The incandescent probably as well.  The LED and incandescent are instant on, the CLF takes a while to build up brightness and get to its final color.  The CLF starts off quite “yellow”, closer to the “warm” light that we are used to from incandescents, but drifts toward the blue, or “daylight”, end of the spectrum after about 10 minutes, when it reaches full brightness.

The light output from the three globes appears, to the unaided eye, to be about equal at the counter-top.  This despite the difference in lumens between the CLF and the LED.  The reason is that the LED directs the illumination downward, rather than spreading it in a full sphere.  For this application, and others like bedside lamps, office reading lights etc., that’s acceptable.  It is not so good if you want all-round illumination, or downward light plus reflected light off the ceiling.  The comparison to incandescent equivalent watts is only a rough approximation.  It depends on the type of globe, frosted or not, and so on.

[Update] The picture above shows the shadow cast by the three lights at the counter.  The black shape is a ruler.  The shadow diagonal to the left is that cast when the incandescent is blocked, but the area is lit by the other two lights.  The shadow diagonal to the right is the equivalent for the CFL, and the shadow coming straight out is when the LED is blocked.  Lacking a proper light meter the shadows can tell us some comparisons.  Despite the lower stated light output, the LED clearly has the most (downward) illumination.  The CFL and incandescent give much the same illumination.  The CFL casts a more diffuse shadow because it is a much larger source than the filament in the clear incandescent.

The LED is dimmable, as is the incandescent of course.  The CFL is not, but dimmable models are available – at a slightly higher cost.

What puzzles me is that the LED has a 5 year warranty vs. the CFL at 7 years, despite the supposed longevity of the LED at a factor of 6:1 over the CLF.  What gives?  The LED should have a 40+ year guarantee.  It’s all academic anyhow – who can remember when or where you bought a light globe 5 years ago – and where is that receipt and the original packaging?

The other surprise is the wattage of the CFL compared to the LED.  The lumens per watt comparison is 57 lumens/watt for the CFL and 48 lumens/watt for the LED.  That’s the other way around to what I expected.  Can I trust the information on the packet?  I should get a meter and check it out properly!  Both feel noticeably cooler (in heat temperature, not color) than the incandescent – as expected.

Let’s summarize the alternative economics, assuming that the consumption and durability claims are correct.  Let’s further assume that we use the globes for a bit over 4 hours a day, or 1500 hours per year.

Cost of electricity per year:

• CFL 14W * 1500hrs /1000 * 16c/KWh = electricity cost/year = $ 3.36
• LED 9W  * ditto =$ 2.16
• Incan.60W * ditto =$14.40

Cost of replacement globe:

• CFL $ 4 * 1500/8000 per year = $0.75
• LED $20 * 1500/50000 per year = $0.60
• Incan. $1 * 1500/3000 (assuming the incandescent lasts about 2 years – about my experience in this bathroom fitting) = $0.50

Total/year:

• CFL $4.11 (yielding a rough (!) payback period – based on purchase price vs. savings over incandescent –  of 5 months)
• LED $2.76 (payback = 20 months)
• Incan $14.90

If we were really anal we would factor in the costs of labor changing the bulb (zero in my case – I lie around the house anyhow), the heat output from the incandescent (positive in winter, negative in summer), disposal costs (need to drive the CFL to the recycle station – who are you kidding?), premature failure of light fitting, wall coverings and paint due to heat from the incandescent….  Let’s just call it even.  And so – surprise, surprise – it makes sense to go with CFL’s, not so much with LED, and certainly get rid of those old incandescents.  If – there is always an “if” – you can live with the color….

What does the ultimate authority, my wife, have to say?  She likes the incandescent color best, can live with the LED, hates the CLF once it gets to final color.  However, she does not complain about the other CFLs in the house.  Is it that particular color? or because she can see, and compare, it next to the soft glow of the incandescent? or because the bath location is where makeup is applied and the warm incandescent is kinder to the complexion?  Probably a combination of all three factors.

[Update] It’s like buying a new car. Before you buy you think that only discerning people drive the chosen vehicle, you see so few of them.  As soon as you buy it, they are everywhere.  Much the same with these comments.  As soon as I finish writing the search engines spew out related topics going years back or just out today.  It appears that this whole light issue needs a bit more discussion.  But before getting into the technical part let’s get one thing out of the way.

No matter what the topic, discussions on the internet degenerate into name calling;

• Leftist extremists/socialist/tree huggers vs. troglodyte/baby seal killing/right wing nuts
• Climate change deniers vs. anthropocentric climate change deniers vs. the rest
• It’s all Gods will vs. the black hole will get us anyhow
• Anecdotal/hearsay/fiction vs. “fact”

I have been hesitant to open the site for comments because of that trend, but will do so anyhow in a short while – will see what happens.

On Salon there is an interview with  Jane Brox, author of “Brilliant”.  I have not read the book, so can’t comment.  But the interview and the comments that follow throw up some valid points:

• We have a negative association with fluorescent light – because we think of the old style tubes in work places, hospitals, cheap housing and other places where we would rather not be.  We have positive memories of the soft, yellow glow of incandescent lights in muted lamp shades.  So color, or perceived color, is a real problem.
• Many claim to get headaches from fluorescents – a claim that may well be correct.  The flicker rate of the old style tubes was at 120Hz, i.e. twice the line frequency (60Hertz – Hz = cycles/second in the US, 50Hz most other places) [Good ole USA – has to be different in this as well…].  Now that is above the rate where the human eye can “see” the flicker.  30Hz seems to be the cut off point, movies and TV systems work at that rate, with some HDTV systems going to 50 or 60Hz.  Of course some people may be more sensitive, and we probably use lights for more hours than we watch movies or TV.  (Knowing some TV and video game addicts that may not be true in all cases).  BUT – the new CFLs flicker at a rate of 40kHz (40,000 times per second) – so any flicker should really be invisible to us.  (See more info about CLF’s at Wikipedia).
• Then we have the mercury issue.  Some bloggers state the CFLs are “full of mercury”.  Hardly!  That there is some is not a good thing, but the technology is improving.  The coal burnt to generate the extra electricity for incandescents is probably higher than that released from discarded CFLs.
• The technology is changing quickly.  A book, like “Brilliant”, just can’t keep up.  Some bloggers comment that CFLs are just an interim step to using LEDs and OLEDs (Organic LEDs) that will change the way we think of lighting, by having whole surfaces emitting light.
• The pedants among the bloggers remind us that incandescents put out heat, and so save on heating bills.  It’s an all-round bad argument.  To use light bulbs for heating is inefficient, not in the right place, and in summer we have to pay for cooling that extra heat.

The realists take on it all?  We now have CFLs everywhere except:

• In the bathroom for the experiment above
• For exterior security lights – because the CFLs won’t come on in low winter temperatures
• In some candelabra fittings, where the form factor just hasn’t arrived yet.

The CFLs are fine.  The only complaint is with some early technology recessed globes that take a minute or so to get to an acceptable light output.  My intent is to go LED (or OLED) as soon as prices drop to less than $10 per bulb