My daughter tells me I waste electricity by leaving things plugged in. She’s been doing an energy audit of her high school (for her science class) and seems to think she’s an expert in energy efficiency all of a sudden. I tried to tell her that it won’t make much difference to unplug everything in our house, but she insists that it’s wasteful to leave things plugged in, and she wanders around unplugging everything in sight that isn’t in use. Is she right or is she taking this too far?

Answer from Green Energy Efficient Homes

Electricity is a form of energy and in a sense all electricity does ‘work’. When you say an appliance might waste electricity what you really mean is that the work the appliance did with the electricity is wasteful. If the appliance doesn’t use any electricity, then there is no waste.

As I explain on my About me page, a number of years ago an engineer sold me a handy Kill A Watt to measure the power usage of plug-in devices, and I discovered that many of my household appliances were using small amounts of electricity continuously, while doing absolutely nothing of value for me. I consider ‘work’ to be something that is useful to me; having five digital time displays in one room isn’t really useful work!

What kinds of work typically waste electricity with plug-in appliances? Some obvious ones are appliances that produce light or heat without any benefit – for example, you might have an LED display on your DVD player or game console that stays lit up even when you aren’t using the device. That is needless work. Or you might feel heat from the AC to DC converter that charges your cell phone or powers the rechargeable dust buster. That heat is a byproduct of the energy conversion, and in and of itself it is wasteful because that heat is not helping charge the phone or dust buster. If the converter stays warm even when the device it is supposed to charge is not plugged into it, then you’re wasting energy on the converter whenever it is plugged in, regardless of whether it’s charging or not.

So you do waste electricity keeping devices plugged in that consume electricity without doing any useful work. But if the plugged in device shows no sign of doing any work (useful or otherwise) there probably isn’t any savings to be had from unplugging it.

In some situations it’s obvious whether leaving something plugged in is wasteful. A simple table lamp that is left plugged in doesn’t waste electricity when the switch is turned off. An electronic device with an LED or other lit-up display is indeed using a tiny bit of electricity to power that display, and sometimes that also means it’s using a larger amount of energy for other purposes (for example, some TV screens have an instant-power-on feature that means the screen stays bright whenever you click the remote, and these instant-on screens can use up to 50 watts even when turned off, waiting for the on signal).

You probably won’t save the planet from climate change or slash your energy bill in half by unplugging appliances that aren’t using any (or much) electricity, but there are situations where you will waste less electricity by turning things off or pulling out the plug. For example, you should probably keep your computer equipment on a power and surge protector bar, and turn the bar off when the computer is not in use. Even with the PC itself turned off, the combined power draw of a cable or DSL modem, a wireless router, and a computer printer sitting idle and waiting for work to do, can exceed 50 watts (about the same draw as one moderately bright incandescent bulb or 4 compact fluorescent bulbs). That might not sound like much but that 50 watts when running continuously through the year works out to 50 x 24 x 365 watt hours, or 438,000 watt hours (438 kilowatt hours). That costs roughly $44 a year – to keep your computer equipment running 168 hours a week, when you probably only need it running for 10 or 20 hours a week at most.

Another way to determine whether something left plugged in wastes electricity is to think what ‘plugged in’ means. In order for electricity to do work there has to be a closed circuit – a continuous two way connection between the power source (your local power plant, hydro dam, solar panel etc.) and the device doing the work. The table lamp that is plugged in allows electricity to reach the light bulb, but only if the light bulb switch is also turned on. The washing machine won’t work if unplugged, but it also doesn’t do any work if you haven’t turned the switch to the start position, which closes the circuit and starts the washing machine doing a load of laundry. So there’s no energy gain to be had from unplugging a washing machine. The same is true with most larger appliances such as dishwashers, dryers, toasters, toaster ovens etc., except that any of these that has a built-in digital clock or other display does use a small amount of power to run the display.

Again, you need to think in terms of ‘work’ being done. If no work is being done, there is no electricity being wasted. If work is being done, then there may be wasted electricity if the work being done is not of benefit.

Examples of work being done that isn’t useful include leaving a light on in an empty room (you should always turn off lights when you leave a room); leaving a cell phone charger plugged into an outlet when the cell phone is already fully charged, or is no longer connected to it, running your router and cable/DSL modem 24×7 even though you only use the Internet for a few hours a week; running the dishwasher when it’s not full; leaving that flashing 12:00 on the VCR or DVD player instead of unplugging it; and so on. In our own house we were able to significantly cut our electricity bill by measuring our energy consumption and disconnecting devices such as the chargers and routers and DVD player when not in use.

You may have heard elsewhere that you should unplug all AC to DC converters, and while I mention it here and have certainly benefited from this in my own house, you won’t necessarily save energy by unplugging every one of them. It’s true that any converter that feels warm or hot to the touch is wasting electricity – the converter may be using electricity even if the device it’s connected to is fully charged, or if there’s no device connected at the time. But more and more manufacturers are providing chargers that can detect when there is no draw on the DC current portion of the circuit, and they will cut energy consumption of the converter to near zero, and I’ve certainly seen this on laptop chargers, which ten years ago would draw a steady 30-40 watt current even with no laptop plugged in; my current laptop charger doesn’t even register on my Kill A Watt meter when the laptop itself isn’t connected. Any device that has a charger or AC to DC converter and that is ENERGY STAR certified probably draws little or no power when the charger or converter is not plugged in.

One good energy saving tool to cut the wasted electricity from these converters is the Belkin Conserve Energy Saving Power Strip, which can detect when a device is no longer drawing much current, and then shuts down the entire set of devices plugged into the power bar.

I commend your daughter for trying to find ways to cut your home energy use, but you might want to remind her to use the same technique at home as she used at school: use the power meter she probably used for the school energy audit to measure the electricity consumption of home appliances, lights and the like, when they are turned off. She will quickly discover that at least some of the things she is telling you need to be unplugged, are not drawing any power at all, while others may only be drawing a watt or two – not really enough to make a differences to your electricity bill.

33 replies
  1. Leebert
    Leebert says:

    So I hardly ever use my laptop but I leave it plugged in (and turned off) to keep the battery juiced. Is this a wasteful thing to do?

    Reply
    • Robin
      Robin says:

      It is probably ever so slightly wasteful. The older the adapter the more electricity it is likely to use. I just plugged my daughter’s Lenovo ThinkPad (1-year-old model) into my Kill A Watt meter, after a full charge, and the charger alternates between 0 and 1 watts every few seconds – presumably because every few seconds it checks to see if the battery will take a charge, finds it won’t, and stops trying.

      Current standards (as of November 2015) are very stringent in terms of the ratio of input energy from the wall socket to output energy to the device, and also in terms of the amount of current draw allowed when nothing is plugged into the charger. The current Level V standard limits draw when no device is plugged in, to 0.5 watts, whereas I remember ten years ago, my ThinkPad charger drew at least 10-15 watts continuously with nothing plugged in. The Level VI standard taking effect in February 2016 further reduces the ratio of input energy to output energy (meaning more of the electricity reaches the device instead of being converted to waste heat), and further drops the no-device level to 0.1 watts.

      The best way to tell is to feel the charger. If it is room temperature it is likely using very little energy. The warmer it is, the more energy it uses.

      It is also not a good idea to leave your laptop plugged in continuously because the battery needs to periodically discharge, typically to 75% or 80%, and then be recharged, rather than always stay close to 100%.

      Reply
    • Robin
      Robin says:

      Without testing it with a Kill A Watt or similar meter, I can’t say. If there is a power switch on it, then it is probably not using much electricity, as new energy efficiency guidelines require devices to use minimal power when switched off.

      Reply
  2. Angela Mcmeekin
    Angela Mcmeekin says:

    Does a reclining chair plug left switched on use power or does it only use power when I press the hand set to make it move? Should I switch it off at the plug to stop power waste or does it only use power when I press the handset or is it the same as a phone charger only using very little poer when not being used but much more power used when I change the position on the chair?

    Reply
    • Robin
      Robin says:

      If by handset you mean a remote control, then the reclining chair would be drawing power continuously waiting for a command from the remote control. It’s likely in the neighborhood of 10-20 watts.

      If the handset is attached directly or by a wire to the reclining chair, there’s likely no power draw except when the chair is actually moving.

      The power consumption from moving the chair will be negligible either way. If the chair has a remote control you could be looking at $10-40 a year in electricity costs just to keep the chair ready for a command from the remote.

      The above is not based on any experience with reclining chairs, just general knowledge of how ‘phantom loads’ work and what kinds of electrical devices draw power continuously vs. only when actively used.

      Reply
  3. natalie
    natalie says:

    Do the refrigerator, water tank, washing machine, television and stove hike the price of your light bill? If so, how can you tell your parents to reduce it?

    Reply
  4. Hanna
    Hanna says:

    What will happen if I unplug my refrigerator daily until I get home from work? Will it not burn more energy to start up than of I didn’t unplug it?

    Reply
    • Robin
      Robin says:

      Refrigerators kind of unplug themselves periodically through the day, because once they reach a low enough temperature the compressor and fan stop, until the temperature goes back up and they kick back in.

      By unplugging your refrigerator you are taking over control of that cycle, and the temperature inside will rise more, which increases the likelihood of your food spoiling. It won’t use more energy than leaving it plugged in – overall it might save you a small amount. But then the compressor will have to run for a longer initial period when you start it up again, and that’s a use pattern the refrigerator wasn’t designed for, so you’ll likely wear your refrigerator out faster.

      If you include the energy it takes to manufacture a refrigerator, and assume that unplugging it each day decreases the life of the fridge from, say, 10 years to 9 years, I would guess that any daily savings in electricity will be more than eaten up by the higher energy cost of making the new fridge a year earlier.

      Reply
  5. spencer
    spencer says:

    what about devices that are not ‘working’ when plugged in, but are powered by a detachable power lead (kettle leads, adapters that do not charge a device)?

    Reply
    • Robin
      Robin says:

      A device that is doing no work draws no electricity. However work can include producing heat or light, so if you sense any heat coming from the device (or the charger for the device) when it’s not working or charging, or see any light coming from it, it may be using a small amount of electricity. Most light produced by home appliances and electronics these days is from tiny LEDs whose power consumption is insignificant, and most power supplies don’t consume any power when the device is not attached to them. However, leaving a cell phone plugged in will consume power even when the phone is fully charged; not only that, you shorten the phone’s battery life by keeping it plugged in when fully charged.

      Reply
    • Robin
      Robin says:

      If you leave your laptop in sleep mode and NOT plugged in, the battery drains fairly slowly (how slowly depends upon the model – my ThinkPad T460s manages to last a whole weekend on sleep mode and loses only about 20% of its battery power). If you leave it plugged in in sleep mode, you may be drawing power continuously. The easy way to check is to feel the power brick and see if it is warm. Anything above room temperature indicates power is being consumed.

      Reply
    • Robin
      Robin says:

      Not only is it a waste, but it is probably bad for the life of your phone battery. Leaving a cell phone plugged in beyond 100% charge shortens battery life.

      Reply
  6. Sonia
    Sonia says:

    What about the extension switches? Do they use electricity when plugged in and are not connected to any other device ?

    Reply
    • Robin
      Robin says:

      I’m not sure what an extension switch is. If you mean an extension cord, it does not use any electricity, all it does is conduct electricity when something is plugged into it.

      Reply
    • Robin
      Robin says:

      If your fan is plugged in but turned off it is almost certainly using little to no electricity. Little if it has LED lights that are on while it’s not working, none if it has no such lights. Even when on, fans use very little electricity compared to an air conditioner so I wouldn’t worry much about how the fan will affect your power bill.

      Reply
  7. Pamela Tan
    Pamela Tan says:

    Will I use electricity if I disconnect my laptop from it’s power cord and just leave the power cord plugged in? My boyfriend does this all the time!

    Reply
    • Robin
      Robin says:

      With the power cords made today, probably not. Ten years ago was a different story. The way to tell is to feel the power cord brick – if it is hot it is using electricity. If not, it is probably not.

      Reply
    • Robin
      Robin says:

      I suggest you check out my How to save electricity article for tips on what to unplug.

      As of 2017 the importance of unplugging chargers and power supplies is definitely less than it was when I wrote this article almost 10 years ago, as new energy efficiency requirements mean that most power supplies must have minimal power draw when they are plugged in but no device is plugged into them.

      Reply
  8. Anatasia Malcolm
    Anatasia Malcolm says:

    Does switching the lights on and off in your house run up the bill? Should I leave it on the whole time until I’m ready to turn it off at night? Or if for example: I’m not in the kitchen for an hour, should I switch it off and whenever I come back within another hour time I switch it on. Can this run up the electricity bill?

    Also does going into the refrigerator often run up the electricity bill?

    Reply
    • Robin
      Robin says:

      I believe I’ve already answered your first question in my Turn off lights article – essentially, it is always better to turn a light off when you leave the room, than to leave it on in case you might come back soon.

      Cold air falls. Every time you open the refrigerator, much of the cold air falls out and is replaced by warmer air in the room. So it’s generally more efficient to decide what items you need from the fridge (e.g. while preparing the meal) and open the fridge once, take everything out, and close the fridge again. This will mean less lost cold air, and therefore less electricity used, than opening and closing the fridge for each item. It’s also better to leave an item out for a few minutes, if you know you’ll be going back in for something else, than to always put every item back immediately.

      Reply
  9. Chris
    Chris says:

    Hi, I have an outside light that comes on say when someone walks outside, my husband keeps turning it off at the switch inside the house because it’s wasting electricity. Is he right, if he is there doesn’t seem much point in having it does there?

    Reply
    • Robin
      Robin says:

      Motion sensor lights use about one watt of power when the light is off (but the switch is on), and they add about five watts of power when the light turns itself on.

      If you know that no one needs the motion sensor light for a period of time, then you’re saving one watt of power during that period. Say, for example, that you only want the light to be activated when you or your husband are outside. If you therefore turn the switch off when you go in for the night, e.g. at 9pm, and don’t turn it on until the following evening at 5pm, then you are saving 20 hours at 1 watt per hour. Over the course of a year that will save 7.3 kilowatt hours, or somewhere around $1-2 per year.

      The bigger savings would come from turning the switch off when you don’t want the light to activate accidentally. For example, some of my neighbors have motion-activated outdoor lights that activate when I walk my dog down the street. I’m nowhere near their house but the light still goes on. So every time I walk by, they’re using a bunch of electricity to light an area nobody is even in, which seems wasteful.

      I’ve read that outdoor lighting for security purposes is actually self-defeating. It looks pretty suspicious to see a flashlight dancing around in someone’s driveway, but a light on in a driveway looks perfectly normal, so by having a motion activated light you are making it easier for thieves to find their way around your property without appearing suspicious. Such lights also contribute to ‘light pollution’ which make life unpleasant for stargazers. In my opinion they are overused. There are cases where they are needed, such as in the countryside where it can be pitch black outside and you want some kind of light to come on when a visitor comes by, but in the city where there is usually ambient light from streetlights, they’re unnecessary. But that’s just me and it’s a free world!

      Reply
    • Robin
      Robin says:

      Touch the phone charger when it is not connected to a phone. If the charger is room temperature, it is probably not using much or any electricity. If it is warm, it is using electricity and you should unplug it.

      The USB chargers I’ve measured only consume electricity when something is plugged into them to charge.

      Reply
  10. Dj
    Dj says:

    Poor Robin, didn’t any of you read the article? You keep asking him questions that would be answered if you would just take the time to read it 🙁 That’s the problem with people today, google has made people lazy. Thanks for the article Robin, I got everything I needed to know from reading (:

    Reply
  11. kannan
    kannan says:

    When I close my laptop it goes to hibernate. My laptop does not have a battery.

    I understand from Windows 10, that in this mode it is as good as shutting down completely.

    Does this consume energy? If so how much?

    Assuming I shut down and no battery is connected but the power adapter is still plugged into the system, does it consume any energy?

    Reply
    • Robin
      Robin says:

      The power consumed by a laptop in hibernate mode or shutdown is strictly power to charge the battery. For some laptops even when the battery is full, you may be using power while it’s plugged in.

      In the case of a laptop with no battery, there is nothing to charge. So unless your power adapter is an inefficient one that always consumes power even when nothing’s plugged into it, you’re not using any electricity when the laptop is turned off or hibernated. The way to tell is to feel the adapter itself when it is plugged in but has not been used to run the laptop for at least half an hour. If it is warm, it is using electricity. If it’s room temperature, it probably isn’t.

      Reply

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