CFL/Fluorescent Efficiency

[jebatty]

I just tested two CFL's on my Kill-A-Watt meter. A new inexpensive one (about $1.00) was rated 11 watts, 200 ma, 120 volts. Another about 10 years old (probably about $10.00) was rated 20 watts, 185 ma, 120 volts. The meter reported the following:

House volts = 122
New CFL: 12 watts, 23 va, 0.19 amps, pf = .53
Old CFL: 16 watts, 18 va, 0.15 amps, pf = .89

The new CFL appears to be much less efficient than the old CFL. Also, the new CFL is using 23 watts/equivalent of power if compared to an incandescent bulb. CFL's are rated at 44-80 lumens/watt, and incandescent are rated at 7-24 lumens/watt. While it appears that the new CFL is producing more lumens/watt than an incandescent bulb, it is not nearly as efficient as I would have assumed, and particularly as compared to the old CFL.

While the lack of efficiency does not translate to watts used, and therefore does not directly impact my electric bill, it seems to me that there should be an understandable standard manufacturers of CFL's, perhaps all lighting bulbs, should be required to label so that a retail customer can easily know the efficiency of various CFL's. Perhaps lumens/va rather than lumens/watt. Although most retail customers probably don't really know what a watt is, they certainly don't know what volt-amps are. So maybe an energy standard of lumens/power unit, or something like that.

A few months ago I bought an inexpensive 2-bulb T8 (34 watt bulbs) fixture to replace an old 2-bulb T12 (40 watt bulbs) fixture. I similarly put the Kill-A-Watt meter on these fixtures. The new T8 had a pf of 0.49 and the pf of the old T12 was considerably higher (don't remember what it was). I thought I was buying a high efficiency fixture, and I'm not sure that the goal was accomplished. I don't know the lumen output of each fixture, so an exact efficiency determination cannot be made.

Lesson learned. In the future when I buy CFL's, I will compare brands of the same watt rating based on the milliamp rating, and buy CFL's with the lowest milliamp rating for the wattage I want.

 

[EatenByLimestone]

Are the bulbs otherwise comparable? Different K? CRI? I don't know much about CFLs but different features may make a hit on efficiency.

Matt

 

[Highbeam]

You're right, most people have no freaking idea what a volt-amp is. I'm an engineer educated in physics and math and have no freaking idea. I buy my electricity by the watt so lumens per watt makes perfect sense.

 

[midwestcoast]

Darnit, here I thought I was getting the hang of understanding efficiency (watts, volts, amps). So what IS a volt-amp then??
Wonder if this is a common thing that newer CFL's have traded some efficiency for the better quality of light (usually) & lower cost they have now.

 

[jebatty]

These lamps did not have any other info on them from which I could tell if there were other differences; just "typical" bulb replacements.

Please don't interpret my comments as anti-CFL based on energy usage. Even a CFL with a .5 PF provides an efficiency advantage over an incandescent lamp, but a CFL with a high PF would be even better. I'm not making any comment on the other +/- issues involving CFL's. We use them in almost light fixtures in our house, and we are satisfied with them and will continue to use them. I'll just pay more attention to actual current draw per watt than before.

 

[midwestcoast]

No worries, no mis-interpretation here. I've been using CFL's for 10 years, have them inn every interior fixture sace one LED & will use them 'till something more efficient comes along. Just noticed that I don't like the light from some of the newer bulbs as much as my oldest ones (of same Kelvin).

 

[DBoon]

I believe the Energy Star rated CFLs must have a high power factor. Not 100% sure.

 

[btuser]

I'd check it with a light meter too. For all we know there's been a burn-in period with the older bulb, and while it may be rated for a particular wattage it may not be sipping that much juice. As it ages, there may be resistance that builds up.

 

[dougstove]

I think a volt-amp would be the power output from an amp of current flowing through a drop of 1 volt.
I am quite frustrated with the big push to compact fluorescents.
i) Most (all?) contain mercury; they are going to be a long-term toxic issue.
ii) In my experience their operating lifetime in many circumstances is much shorter than rated.
iii) In my climate (heating or borderline heating for 8-10 months per year), the emphasis on electrical efficiency is a bit overdone. An inefficient electric appliciance, within reason, is just contributing to the basal heat of my house. I can see that in Arizona etc., where the main issue is air conditioning, lowering waste heat output is a good goal.

I am looking forward to the onset of practical LED lighting; some of the stuff we have in the lab is very impressive already. I think the CFL fad will be transient.

 

[jharkin]

If you want to get even more confused: http://en.wikipedia.org/wiki/Volt-ampere

Bottom line I think is that the distinction between VA and Watts is because of inefficiencies in AC devices that prevent some of the drawn power from being used to produce useful work. The apparent power (VA) is what you can measure, the real power (watts) is what does work in your device. The difference is the power factor and gets wasted as heat in the wiring I think.

Or at least that is my simplistic understanding. The real reasons have to do with phase angles and the differences between resitive inductive and capacitive loads and you really do need to be an EE to understand it all (Im not, I dont)

 

[mayhem]

Over time, fluorescent tubes and CFL tubes will degrade. I bet the 10 year old bulb used to draw 22-24 watts when new and that it was bit less yellow than it is now.

 

[woodgeek]

IMO, ignore the VA and the PF. Contrary to what some charlatans will try to sell you (power conditioners) the wiring losses due to pf<1 are completely negligible.

You get charged for Watt.hrs, that is all you need.

 

[Later]

While the power company calls the power used watts, it might be actually be VA.

 

[jeff_t]

Don't now how efficient they are, but they're cheap-my local Ace has GE CFLs for $.99 thru the end of the month. 10-13-20-26 watt sizes. I bought thirty of them today.

 

[BrotherBart]

Don't now how efficient they are, but they're cheap-my local Ace has GE CFLs for $.99 thru the end of the month. 10-13-20-26 watt sizes. I bought thirty of them today.

Yeah I stocked up at ACE last week. A sure sign that I will find them somewhere for a quarter next week. :-S

 

[btuser]

The mercury concern is over-blown. When you consider the amount of electricity saved by the bulbs even irresponsible disposal can't compare with the amount of released through the burning of coal. The thermostat (non digital Honneywell round) on my wall has about 3000mg of mercury. That's enough for about 7,000 of these dreaded bulbs!

http://en.wikipedia.org/wiki/File:Mercury_emissions_by_light_source_EPA_2008.svg

 

[Vic99]

Like the link. Good find Btuser.

 

[DMX_512]

Here is a pretty good link that will give you about all the info you really need to know about a given lamp. You just need to know the ANSI code for the lamp. It is a 3 letter designation plus some other info that is generally stamped/printed on the lamp base.

CFL lamp

 

[midwestcoast]

Good info here. So I'm still not too sure I understand VA vs Watts, but I've now decided I don't need to know %-P
You all did get me curious to see what my 9, 11, 15 watt CFLs actually draw, so I went around to a few with my knock-off Killa-a-watt & found......wait for it..........they pretty much draw the wattage they're marked at :smirk: Didn't find any age correlation. I did find a couple that are marked 15W & draw only 11-12. Sweet.

I too am of the opinion that CFLs are pretty good tech even if they contain a small amount of mercury. I find they last a loooong time with the exception of outdoor fixtures & fridges (lot's of on/off & cold temps). It'd be better if safe disposal options were more developed & promoted though, and I have broken 2 & got the heebeejeebees while sweeping up the mess. Wonder how many people fire up the vacuum & spread the vapors all through the house?

On the topic of inefficient lights contributing to home heat I'd argue they're rather inefficient heaters as well whenn you consider the normal twisted route the power takes to becoming heat/light in your home: Coal/oil/gas extracted & burned to create steam, steam turbine to create electricity, transfer & loss in power lines & transformers, then through an element where resistivity creates heat (& relatively little light). Now place that heat ouput up near the ceiling where it does less good, or even worse, in a recessed fixture venting to the attic/floor joist and you've got a pretty sad home heating device.
Take that same coal/oil/gas & burn it efficiently in the home & you'll benefit from much more of it's heat energy.

 

[btuser]

I'm not against electric heat. It makes it pretty easy to zone your usage, and there's very little system loss if you're only counting the home and not plant transmission losses. Problem is heat from a lightbulb is still heat from a light bulb whether it be Winter or Summer.

After a few more hundred nuke plants we'll all be wishing we had electric heat. Electric sooooooo cheap you don't even have to meter it!

 

[DMX_512]

I still have yet to understand why LED medium base lamps are not being used more. LEDs are making huge strides in the theatre and entertainment industry. The mark-up on LEDs is outrageous though. However, they are dim-able, no mercury, and the color temperature of the light can be shifted (3200 deg K with a little amber and 6500K-daylight- with a little cyan). I regularly use LED theatrical units that have a light output very close to a 575 watt lamp / unit. The LED lights are drawing about 100 watts max.

 

[berlin]

"The mercury concern is over-blown. When you consider the amount of electricity saved by the bulbs even irresponsible disposal can’t compare with the amount of released through the burning of coal. The thermostat (non digital Honneywell round) on my wall has about 3000mg of mercury. That’s enough for about 7,000 of these dreaded bulbs!"

Even the burning of coal produces a very tiny percentage of atmospheric mercury compared to natural and other anthropogenic sources; much smaller than many alarmists would have you realize: http://img.medscape.com/fullsize/migrated/522/270/mgm522270.fig1.gif

 

[DMX_512]

I agree that the amount of Mercury in CFL's is not a major household threat. I just feel that LED's are a far superior technology.

 

[Gooserider]

I agree that the amount of Mercury in CFL's is not a major household threat. I just feel that LED's are a far superior technology.

I agree that LED's are superior from a technology standpoint, or at least have the potential to be, but at this point they just aren't cost effective for most applications - I'm really not sure why other than manufacturers charging so much that they are killing sales - but if so, that begs the question of why nobody is breaking into the market selling LED products at a more reasonable cost?

Part of it, I think is that while LED FIXTURES can be designed to be as good as incandescent / CFL fixtures, in output, they really haven't gotten a good handle on how to do a nice replacement bulb for most standard lights that puts out a competitive amount of lumens / watt...

Gooserider