# alternating current (AC) **URL:** \ **Category:** Factual Questions\ **Created:** [November 27, 2008, 6:58pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727 "2008-11-27T18:58:18Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![yoozer](https://avatars.discourse-cdn.com/v4/letter/y/e480ec/32.png) [@yoozer](https://boards.straightdope.com/u/yoozer)\ **Post date:** [November 27, 2008, 6:58pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/1 "2008-11-27T18:58:18Z")
I am told my cellular phone charger draws AC even when the phone is fully charged/ unplugged. What about an electric razor or a powered lamb with burned out bulb? Thanks, Pat Doherty aka yoozer ---
**Author:** ![yoozer](https://avatars.discourse-cdn.com/v4/letter/y/e480ec/32.png) [@yoozer](https://boards.straightdope.com/u/yoozer)\ **Post date:** [November 27, 2008, 7:00pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/2 "2008-11-27T19:00:03Z")
powered lamp! ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 27, 2008, 7:03pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/3 "2008-11-27T19:03:21Z")
If anything’s drawing current in your cell phone charger, it’s the transformer. Basically, everything with a big fat “wall wart” plug has a transformer in it (which changes the 120 volts from the wall to whatever the thing plugged in needs, and usually also converts it to DC), but electric shavers and lamps typically run off the wall current directly, so they don’t have transformers. The amount of draw for an unplugged charger should be negligible, though. Feel the casing of the wall wart: Any wasted electricity will be turned into heat, so if there’s a significant amount of wastage, it’ll be warm. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 27, 2008, 7:05pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/4 "2008-11-27T19:05:41Z")
Generally, simple, non-electronic appliances such as toasters and standard incandescent lamps don’t draw standby power when plugged in but turned off. Most electronic devices contain transformers which do draw small no-load current whenever they’re plugged in; many modern devices also use some small amount of power to keep internal clocks running or keep circuitry waiting for input (a key press, a remote control signal, a temperature change or what have you) operating. If you’re looking to conserve as much energy as possible, when in doubt, pull it out. The savings gained this way are typically small, but it all adds up over time. ---
**Author:** ![yoozer](https://avatars.discourse-cdn.com/v4/letter/y/e480ec/32.png) [@yoozer](https://boards.straightdope.com/u/yoozer)\ **Post date:** [November 27, 2008, 7:11pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/5 "2008-11-27T19:11:14Z")
Thanks and happy Thanksgiving Chronos and Q.E.D. You have made it sound simple. PD ---
**Author:** ![633squadron](https://avatars.discourse-cdn.com/v4/letter/6/ee59a6/32.png) [@633squadron](https://boards.straightdope.com/u/633squadron)\ **Post date:** [November 27, 2008, 7:19pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/6 "2008-11-27T19:19:04Z")
> [@yoozer](#): > > I am told my cellular phone charger draws AC even when the phone is fully charged/ unplugged. What about an electric razor or a powered lamb with burned out bulb? Thanks, Pat Doherty aka yoozer In general, if it has a power brick or power supply, it’s drawing some current. The easiest way to tell is the power brick, the big (usually) black box that you plug into the back of the whatever with a strange looking cord. The brick has another cord that plugs into the wall. Anything that is still lit when it’s “off” is drawing power, including power strips, computers (leds lit?), TVs, TiVos, stereos, game consoles, “electronic” appliances, and so forth. You probably don’t save much by turning these off when you go off to work in the morning, but you might want to shut them when you leave on a vacation. ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [November 27, 2008, 10:20pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/7 "2008-11-27T22:20:01Z")
> [@Chronos](#): > > The amount of draw for an unplugged charger should be negligible, though. Feel the casing of the wall wart: Any wasted electricity will be turned into heat, so if there’s a significant amount of wastage, it’ll be warm. And even if it is warm to the touch, that doesn’t mean the losses are significant - it only takes a tiny amount of heat to keep that lump of plastic a few degrees above ambient. I’ve seen measurements carried out on a number of such plug-in transformers - the draw was in all cases significantly less than 1 watt. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [November 27, 2008, 10:43pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/8 "2008-11-27T22:43:37Z")
As for shavers, if they have a rechargable battery in them, then there is some current draw to maintain charge. ---
**Author:** ![King\_Solomon\_Hill](https://avatars.discourse-cdn.com/v4/letter/k/59ef9b/32.png) [@King\_Solomon\_Hill](https://boards.straightdope.com/u/King_Solomon_Hill)\ **Post date:** [November 27, 2008, 10:57pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/9 "2008-11-27T22:57:14Z")
A lot of devices use [switchmode power supplies](http://en.wikipedia.org/wiki/Switched-mode_power_supply) these days. I’m not sure that they draw zero power when plugged in but not in use, but I know it’s a less than an old coil transformer. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [November 28, 2008, 3:59am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/10 "2008-11-28T03:59:13Z")
BTW, these sort of small electrical leakages are known as “phantom loads” to the off-grid crowd. If you went around your house and added them all up, you might be surprised about how much power they consume. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [November 28, 2008, 4:02am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/11 "2008-11-28T04:02:40Z")
> [@yoozer](#): > > powered lamp! There is an [Electric Lamb](http://electriclambstory.blogspot.com/). ---
**Author:** ![Leaffan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leaffan/32/299_2.png) [@Leaffan](https://boards.straightdope.com/u/Leaffan)\ **Post date:** [November 28, 2008, 4:15am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/12 "2008-11-28T04:15:37Z")
> [@beowulff](#): > > BTW, these sort of small electrical leakages are known as “phantom loads” to the off-grid crowd. If you went around your house and added them all up, you might be surprised about how much power they consume. Yeah. Maybe 20 bucks a year. :rolleyes: ---
**Author:** ![groo](https://avatars.discourse-cdn.com/v4/letter/g/ecd19e/32.png) [@groo](https://boards.straightdope.com/u/groo)\ **Post date:** [November 28, 2008, 5:06am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/13 "2008-11-28T05:06:19Z")
Way back in history, in the time before 9/11, President Bush held news conferences warning about these [**energy vampires**](http://www.gcn.com/print/vol20_no19/4635-1.html?topic=news#). I keep all of them on a power strip, so I can disconect them with a flick of a switch. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [November 28, 2008, 5:30am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/14 "2008-11-28T05:30:35Z")
> [@beowulff](#): > > BTW, these sort of small electrical leakages are known as “phantom loads” to the off-grid crowd. If you went around your house and added them all up, you might be surprised about how much power they consume. I started switching my computer/entertainment system off at the power strip when I left the apartment, and it cut my bill by 5-10%. I got a rebate that year from Toronto Hydro! (The other big difference came when I replaced my two CRTs with one big LCD monitor, and replaced the tower PC with a laptop, but that was a bit later.) Yes, individually, each phantom load is not large, but there’s often a lot of them, and they’re on all the time. It adds up. People who go off the grid are fanatical about eliminating them, because they tend to do things like draining the house batteries in the middle of the night. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [November 28, 2008, 6:12am UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/15 "2008-11-28T06:12:26Z")
> [@Leaffan](#): > > Yeah. Maybe 20 bucks a year. :rolleyes: Like he said, you’d [be surprised](http://www.bankrate.com/brm/news/sav/Jul07_phantom_load_a1can.asp). ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [November 28, 2008, 2:54pm UTC](https://boards.straightdope.com/t/alternating-current-ac/474727/16 "2008-11-28T14:54:16Z")
> [@Santo\_Rugger](#): > > Like he said, you’d [be surprised](http://www.bankrate.com/brm/news/sav/Jul07_phantom_load_a1can.asp). From that link: > [@](#): > > …if you have 25 power vampires consuming an average of seven watts each, they will cost you $175 per year and emit about 2,000 pounds of CO2. I have no more than 2 chargers plugged in all the time. And if **hibernicus** is right, > [@](#): > > I’ve seen measurements carried out on a number of such plug-in transformers - the draw was in all cases significantly less than 1 watt. …that computes roughly to less than $24 per year at 10 cents per KW. I think I’ll leave mine plugged in. The wear and tear on the plugs, sockets, and my hands is worth $24.