Do chargers use electricity when they aren't being used?

July 28, 2006 4:26 PM

ChargerFilter: Do chargers for things like mobile phones, digital cameras, camcorders etc. use power (and cost money) if they are left plugged in?

Would it be worth unplugging them all (or switching of the plug board/power strip) they are connected to?

This thread almost answers the question (see the last comment)

posted by Glum to home & garden (21 comments total)

are they warm when you touch them? then yes.
posted by cellphone at 4:33 PM on July 28, 2006

Cost money? Can't be more than it would cost to turn on an overlight light for two minutes to find the outlet to re-plug them into if you were unplugging them all the time.
posted by kcm at 4:47 PM on July 28, 2006

In theory they could draw a tiny amount of current. but it's unlikely that they would ever cost more then a few cents a year.
posted by delmoi at 4:58 PM on July 28, 2006

You mean they're not plugged into the device, just the wall? No circuit = no power flowing.
posted by knave at 5:18 PM on July 28, 2006

knave: In the ideal case that's true, but the ideal transformer is just an approximation. Wall adaptors do use power even if nothing's connected to them. Some may use very little, but others are woeful energy wasters. If it's at all possible, unplug them or switch off the outlet they're on.
posted by fvw at 5:22 PM on July 28, 2006

The answer is yes. California is even working on (or has it passed?) a bill called the "California Vampire Slayer Act of 2006" to address this issue.

The little transformers will be warm to the touch even when nothing is hooked up to it. This is the electricity being converted to heat.

If you want to monitor the power usage of your transformers or any plug-in devices try getting a power meter.

You might be amazed at how much power your TV draws when it's "off" and waiting for you to hit the power button on your remote.
posted by lockle at 6:15 PM on July 28, 2006

Great question! Based on the thread you cite I have been thinking the same thing but have not found a cheap power monitor to check it. Hoepfully biffa is reading this and will enlighten us with more detailed data.
posted by caddis at 6:20 PM on July 28, 2006

Yes. An EE and I tested a car ipod charger to find out exactly that. Its very little energy (not enough to drain your battery) but it does use energy. I wouldnt be surprised if all the adapters in a typical home add up to more than a few cents of power a month.

I just asked Dr. Wernher von Braun here in hell and he agrees, "If its hot its using power."
posted by the ghost of Ken Lay at 6:40 PM on July 28, 2006

There are three types... AC output, unregulated DC output and regulated DC outputs.

They use more power when they are charging something (or just operating it) than they do when the charge cycle is complete

How much? Depends on the transformer type and its internal circuits. Some are just transformers... usually step downs. (These are AC output units.) They present a load that is mostly just the resistive portion of the primary side.

The other types, the ones that are DC outputs, contain rectifiers and sometimes regulator circuits. This type would dissipate more power than the AC output types because there are parts on both sides of the transformer... the primary and secondary sides.

You might hear the term 'phantom power' used to describe this minor drain.

Taken in small quantities, they mean very little. Your whole house's worth might only cost a buck or two a year. Taken as a nation of 100,000,000 houses, they collectively suck a LOT of power that does nothing useful.

Environmentally, it makes sense to turn them off and the world would benefit if we did. Micro-economically, it makes no sense to turn them off.

(Nothing is free, BTW. I recall my late wife being amazed when she asked me how long batteries in her radio would last and I told her it depended on how high she set the volume. Same with car headlights... driving with them on costs energy.... minor but measurable.)
posted by FauxScot at 6:54 PM on July 28, 2006

There is another related question: Minimizing the electricity drain of plugged-in items?

As I said there, see how hot it gets. It is important to remember though, the method is seriously complicated by surface area and air flow. Make sure you consider how large the thing is, and how much air circulation there is around it.

Rough guess, if a normal sized power brick (3"x3"x3"?), in stagnant air, is warm to the touch, it is probably wasting at least 5 watts - that is 44kWh/year..
posted by Chuckles at 7:08 PM on July 28, 2006

The Kill-A-Watt is the cheap power meter you ask about. I have the feeling the original poster was asking if they drew as much power as if they were being used, and the answer is no, but the answer is yes if they are asking if the power draw is non-zero when simply plugged in and not used.
posted by kcm at 8:47 PM on July 28, 2006

Some numbers, from devices I have at hand (measured with a Watts Up Pro):

Kyocera wall-wart cell phone charger, 5.2VDC, 400mA: 1.4 watts while not charging, 5.8 watts while charging.

Sony power brick AC-L15A charger for my camera: no measurable draw when disconnected from camera, around 8 watts while charging.

Linksys wall wart for a WRT54G, 12VDC, 1000mA: 2.4 watts alone, around 6 watts during operation.

Titanium Powerbook power brick: no measurable draw while disconnected from laptop, around 20 watts just now (but battery is fully charged, so it's just the operational draw).

Recoton multi-voltage wall-wart power adapter: between 0.8 and 1.1 watts under no load.

Nikon camera battery charger: 0.8 watts when the wall wart is plugged into the charging base but no battery is inserted. No measurable load when disconnected from the charging base (which has an LED on it)

Sony wall wart for a minidisc recorder, 6VDC, 800mA: 1.8 watts alone, 6.3 watts while charging MD's battery.

So if I left the minidisc charger plugged in and forgot about it for a year, 1.8 watts times 8760 hours in a year is about 16 kilowatt-hours (or 56,764,800 joules). At my current electricity rate, that's around $1.25 for the whole year (assuming that the power brick doesn't draw more as it heats up, which it very well might). Now consider that I probably have 20 wall warts like that, and there are umpteen million of me in the US alone.
posted by hades at 10:37 PM on July 28, 2006 [3 favorites]

I dug around some and found a few more wall warts to check. All of these except the last were tested under no load:

Tamura AV9V 800mA: 1.9 watts.
Recoton 10V DC, 850mA 1.9 watts.
Sony 12V DC, 300mA: 0.9 watts
General Electric 14V DC, 700mA (from an old answering machine, I think): 2.4 watts
No-name 7V DC, 300mA: 1.6 watts
Broadxent 16V AC, 750mA (from a DSL bridge): 2.2 watts
Nokia 3.7V DC, 350mA: no measurable draw
ENG 6V DC, 250mA: 1.1 watts
Netgear 7.5V DC, 1A: 2.6 watts unloaded, 4.4 watts while powering a 5-port ethernet switch.

And a Radio Shack 13.8 VDC, 3 amp bench supply: 6.5 watts (much of which presumably goes into the light in the power switch) when switched on but under no load
posted by hades at 10:55 PM on July 28, 2006

Smaller and lighter wall adapters have switching power supplies in them (probably what FauxScot meant by regulated DC), rather than traditional 60Hz transformers.

hades, can you correlate the higher numbers with the old heavy 60Hz adapters, and the lower numbers with switching power supply adapters? It should be the case, but it would be nice to have data, as informal as it is.
posted by Chuckles at 11:22 PM on July 28, 2006

Hades, those are interesting numbers for wall warts. I'd be interested in knowing the numbers for the "off" power for a TV, set-top box, stereo receiver, microwave, desktop PC and CRT. I bet they add up to a lot.

The California Energy Commission (CEC) standards that Lockle mentioned should reduce the wasted power. CEC FAQ.

Old supplies use linear transformers that consume a couple of watts when idle and waste about 50% when in use. These are your typical 3-inch cubes that feel heavy because of the large transformer. The newer ones are about the size of a package of dental floss and feel much lighter. They use switching power supplies. By the new standards they use only 0.5 watt when idle and must be at least 85% efficient in operation.

New audio-video equipment must use only 1 to 4 watts when in standby, compared to the typical 15 watts for older equipment.

The state of California estimates that they can save almost 190 million KWh per year, equivalent to one power plant, just from external power supplies alone. Improving the standby power for audio-video equipment should save even more.
posted by JackFlash at 11:36 PM on July 28, 2006

I have been thinking about this, I am in the process of making a solution for myself. I am going to use an old power box for a computer, the type that had a switch for each outlet (monitor, printer, computer and 2 acessories). This way all my chargers (cell, laptop, cordless drill...) are in one place and I don't have to unplug them each time. I posted the first part of the construction here, maybe this askme will prompt me to take some pics of the finished product.
Also, this askme is about power strips with individually switched outlets.
posted by 445supermag at 8:19 AM on July 29, 2006

Chuckles, I was actually surprised by some of the results. The powerbook supply feels dense to me; I expected it to waste power while not plugged in. The same goes for the Nokia charger, which is about the same size and weight as the Kyocera charger. (It could be that the Nokia charger simply doesn't work; come to think of it.) The Sony and Nikon devices which didn't have any measurable draw while not doing anything were indeed the lighter switching style, though.

I'll see what kind of readings I get from various appliances and such a little later.
posted by hades at 11:02 AM on July 29, 2006

Even though the laptop charger is dense, it is almost certainly a switching power supply. They have get a lot of power output from a small package, so they end up being pretty heavy.
posted by Chuckles at 12:03 PM on July 29, 2006

Easy solution I use if you can charge all your devices at the same time, overnight: Plug all the chargers into a power strip. That way you can just shut it off in the morning and not have to unplug everything, or just pull the one plug from the wall.

If you need more room on your powerstrip, get Power Strip Liberators from Cyberguys.
posted by IndigoRain at 5:01 PM on July 29, 2006

445supermag - better make sure you take the lightbulbs out of the switches. If hades is right about the 3w draw his RS supply draws just from a bulb then you could eat up a notable amount of your savings with just the main ON switch...

For that matter, I wonder how much increased load the wire and switches adds? hades, ever try plugging something into that measuring device with and without a, say, 20' extension cord inline?
posted by phearlez at 2:41 PM on July 31, 2006

Unlikely anybody's reading this any more, but it turns out that the light in the power supply really wasn't drawing much. I've got a power strip with the same type of light in its switch, and there was no measurable draw when that was plugged in and turned on.

I'm curious about the extension cord question myself, now. I'll try that.
posted by hades at 6:07 PM on October 4, 2006