This is a follow-on from the Jan 22 - Feb 2 2007 posts: I have measured the cable modem and several more CFL bulbs and a fluorescent fixture. I'm seeing that CFLs consistently consume 150% to 200% of the power that their packaging claims.
My household "almost always on" total now runs up to:
0.12W neon night light
1W: cell phone charger
3W: motorized lamp timer
4W: weather station
4W: night light
5W: two laptop-computer charger units (while not connected)
5W: three strings of LED christmas lights (OK, it's seasonal)
8W: CFL 10-watt drawing 16W at 50% usage
10W: phone answering machine
12W: alarm system control box
15W: Linksys 802.11a/b/g cable modem/switch
25W: Motorola cable TV box (digital, no DVR, no HD)
92W total thus far.
More Measurements:
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- Device: Linksys (Cisco) WCG200-CC Cable modem and 4-port switch, circa 2004. Has a corded transformer/supply rated 120V 25W, output rated 12VDC @ 1A.
- Current: measured about 121 mA AC once powered-on initialization is complete.
- Power: 14.5 W.
- Usage: This typically is plugged in 24/7/365.
Having a computer online and active on the internet didn't seem to impact this device power by more than 1mA.
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- Device: Compact Fluorescent Lamp (CFL) "floodlight" GE FLE15/2/R30SW. Rated on the package as "15 W".
- Current: First second: 1000 mA inrush, almost no light for first 2 seconds.
215mA at 3 seconds. Light is dim.
178mA at 30 seconds
184mA at 2 minutes
192 mA at 3 minutes.
202mA at 5 minutes (change scale to 2000mA on meter)
205mA at 7 minutes = 24.6W
198mA at 12 minutes = 23.8W
194mA at 18 minutes. = 23.3W - Power: Power draw was very dependent on elapsed time, but seems to stabilize towards 23 W.
- Usage: This is in a fixture over the kitchen sink. Can be left on overnight, or just for minutes.
Once again, worth noting how the real power draw of 23W is 150% of the claimed 15W draw, and the bold packaging mis-states both the actual printed rating and the actual measured rating.
This is also one of those old-school CFL's with an annoying property: it takes a second or two for the lamp to produce any light, and even in the first minute of use it is noticably dim compared to when it's left on a few hours. This is marketed as a replacement for the interior "R-30" 75-W flood light used in recessed ceiling fixtures.
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- Device: CFL "twister" bulb, Lights of America 2009AN9W. Rated on the package as "9 W". Fine print on the bulb base says 140mA at 120V, which would equate to a 16.8W rating.
- Current: First second: 625 mA inrush, but produces some light right away.
126mA to 133mA range over a ten-minute warm-up period.
126mA stable after warm-up. = 15.4W - Power: Power draw was very dependent on elapsed time, but seems to stabilize towards 15 W.
- Usage: This is in a table lamp in the living room that is a "security light" on a timer, turned on half the day.
Once again, worth noting how the real power draw of 15W is 166% of the claimed 9W draw, and the bold packaging mis-states both the actual printed rating and the actual measured rating. This older bulb tends to go dim-to-bright but not as badly as the CFL floodlight above.
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- Device: fluorescent single tube ballasted fixture, one tiny tube type "F14T5" measuring 22" long and about 1/2" diameter. Rating plate says 14W.
- Current: First second: 500 mA inrush, produces bright light right away.
230mA after 1 minute. Second fixture was measured, draws 212 mA. - Power: Seems to be about 27 W.
- Usage: Two of these are mounted under the kitchen cabinets, and I use them a lot so I can turn off the bright overhead floods.
Once again, worth noting how the real power draw of 27W is 193% of the claimed 14W draw, almost double. This was purchased at Home Depot, and I don't know what the original packaging claimed but I'd bet it was 14W. This is a fixture purpose-built to mount under cabinets and light a countertop. The bulb is an odd compact size, the smallest of the tube bulbs that I have seen.
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So what explains the CFL discrepency?
Is this a measurement artifact? One could wonder if the manufacturers present a lying "come on" to get consumers to switch. No doubt the bulbs still draw less current per lumen compared to incandescent bulbs. So why under-state the CFL power consumption across the board?
Like fuel economy in cars, the flaw could be in the measurement method. RMS (root mean square) is one measure that can be used to quantify AC current draw. My DMM measures RMS AC current for a proscribed range of frequency and waveform types: the easist to quantify is sinusoidal current draw and a moderate frequency like 60Hz. CFLs have more than a transformer: their circuit could contribute other components besides 60 HZ to the load, and the load profile may not be sinusoidal. Maybe they rate the current component drawn only at 60 Hz (the name plate says rating 14W @ 120VAC 60Hz) and ignore higher-frequency components for "rating purposes." (To verify this: osciloscope across the current-measuring device would give a dv/dt profile of the di/dt).
The utility meter on my outside wall is the ultimate judge of how much current I pay for. Does the utility meter measure AC current the same way the DMM (RMS) does? If not, would the utility really "give away" up to 50% of my residential electric usage, and over-tax their network by delivering more power than they are metering? I doubt it.
If the utility meter responds to these loads in a manner similar to my DMM, then I simply need to take the packaging in CFLs with a grain of salt, a 150% grain to be exact. I still will wonder what consumer-law loophole allows manufacturers to advertise a rating that is inflated an average of 50%. Because CFLs justify a higher cost by claiming a savings in electricity: that savings may or may not be all it's chalked up to be. The utility meter is the master of my dollar.
Wal Mart recently announced (NY Times Dec 2006 - Jan 2007) a major initiative to sell CFLs in its stores, at lower cost, and "push" the devices out to consumers who, to date, stubornly continue to buy incandescent bulbs. This is often a "high initial cost" issue for their customers, so Wal Mart wants to bring the ASP of CFLs way down from current levels. So I think however this rating thing pans out, it is worth getting to the bottom of the "ratings game" that seems to be going on here. If customers step up to pay for a higher-cost CFL, it would be nice to know the true savings.
