Andy S
Lv 6
Andy S asked in Science & MathematicsEngineering · 1 decade ago

Do appliances consume energy when they're plugged in but turned off?

I'm getting conflicting information on the subject. Logically speaking I might think something with a digital display would draw a bit of power. However, some sources are telling me even things like toasters draw some energy when turned off. Even if they draw energy is it enough that I should consider unplugging them when not in use? Are we talking about energy amounts so small that it's hardly worth the effort. Please quantity for me if possible. Thank you.

9 Answers

  • 1 decade ago
    Favorite Answer

    Some appliances do use small amounts of power.

    Instant ON, televisions have the tube electron gun always warm, so it can produce an electron stream very quickly when you press the POWER button.

    An old toaster, with no other electronics doesn’t use any extra power, off is off.

    Regular old light bulb lamps don’t use any extra power.

    But many appliances have front panel power buttons, that are monitored by a small micro-controller on a circuit board.

    When it detects you pressing the button, it pulls in a large relay, and powers the rest of the appliance. This circuit board requires a power supply, which means transformer is required across the line 24x7. This operates the small power supply, micro-controller etc. To save cost, the main power supplies needed for the appliance are on, up an running, which un-necessarily consumes power. They draw more power when the appliance actually operates, but the idle currents can be substantial.

    However, many small appliances have wall transformers that operate the small appliance. The transformer itself ideally doesn’t use power, but there are losses which do cause these transformers to use some power, and I suppose it can add up. Feel the wall transformer, it is warm, due to the losses in the transformer.

    You are paying for that heat.

    Feel the back of your TV, or other appliances. They are probably warm, even when off.

    One reason people are getting excited about this, is because of global warming, pollution, and the waste of energy.

    In a house full of appliances, stoves, stereos, wall adapters, chargers, AC heating controller, VCRs, DVDs, game systems power supplies, PC sound system power supply, TVs, PC power supplies ( yes they produce constant power even when off), etc.

    I would expect it to total about 100W. ~ $10 per month

    0.15* (100W*24*30)/1000 = $10.80

    15cents per kw times watts used per month divided by 1kW.


    A transformer, is just a large coil of wire sitting across the power line. It would be a short circuit, except that the coil is wrapped around an Iron core which concentrates the magnetic field energy. It would quickly reach its maximum magnetic storage energy limit ( saturation), but the power line is AC ( alternates the voltage direction 120 times per second ( 60Hz) ). This causes the magnetic energy stored from the line power to collapse back into the line 120 times per second. So energy is briefly stored in the iron core, but a few milliseconds later, is dumped back into the line. It is designed as a resonate circuit element at the 60Hz line frequency, so the energy comes in, but goes back out in resonance. If the appliance needs power, it is siphoned off from the magnetic core, into a second winding coil, and doesn’t return to the line.

    Losses occur in the resistance of the winding, and also in eddy currents in the core material that are dissipated as heat.

    This is why the transformer gets warm, and why it looses power when not in use.

    Transformer Core:

    The core material is made of ferrite, which is iron powder mixed with Silicon, which makes it much less conductive. This reduces the eddy current losses, because to the higher resistance of the core, limits electrical current (power) being wasted in the core material. ( This has nothing to do with the electrical current in the two Copper transformer coils.)

    The core is also broken up into thin slices like a pre-sliced block of cheese. The slices are insulated from each other, so that they can not sustain that current path between themselves, reducing eddy current losses. Eddy current losses increase with the square of the applied frequency, so lower frequencies are better to reduce loss for that reason. The problem is that the core then must be very large to hold enough magnetic energy to support the appliance during the slow 60Hz cycle. This means that a 500 Watt power supply may be almost too heavy for many people to lift.

    For this size reason, modern power supplies are designed to "switch", and oscillate at very high frequencies ~ 70kHz, to 500KHz, so that the size of the core can be very small, but transfers that small amount of power at a much, much faster rate. It is like trying to fill a bath tub with a 5 gallon bucket of water once per minute, or using a Dixie cup at a rate of 5,000 per minute.

    This means you don’t have to carry around the large 5 gallon bucket where ever you go, only the Dixie cup. Your power supply can be very, very small, yet produce large voltages, current and power. As a consequence, modern appliances are light weight, and can use almost any battery voltage. The required voltage is "switched up" or down to the needed voltage and current.

    May the force be with you. . .

  • 4 years ago

    From what you describe I would have to say the AC is drawing the most power and I will tell you why. All the the other equipment in your home seems to be of the type that lets off heat. In order to cool the food the fridges expel heat from the back - extra load for the AC. The deep freeze is the same - though not to the same degree is the lid is kept closed and it is not working hard. Stove lets off heat when it is on. Incandescent bulbs let off a lot of heat and cost more to run due to that. ( In Canada the recommend CF bulbs in Summer and IC bulbs in the Winter.) Computers let off heat. If you deal with fridges you likely deal with food which means that you likely run a lot of hot water also ( may be gas), this still heats the air and adds humidity that the AC has to work against. I would tackle the lights both by type and the amount they are on, then turn the AC to dehumidify rather than full AC and put up with a bit of heat until the real hot days. You may be surprised how comfortable the warm air is without the humidity.

  • 3 years ago

    Appliance Power Consumption

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  • 4 years ago

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  • 4 years ago

    Sounds like you are well informed. What if I plug my laptop into a surge protector strip and turn the toggle switch to off- would that be the same as having it unplugged from the wall plug? Thanks!

  • MVB
    Lv 6
    1 decade ago

    Yes, most appliances today draw SOME standby current. If it has a clock (stove, etc), or a light (computer and peripherals), or if it's waiting to respond to a remote (TV, CD, etc) then it's drawing power.

    Also, any item that uses a "wall-wart" transformer, even if it's turned off, the transformer will draw a tiny bit of power. Anything that hums or gets the slightest bit warm, even when "turned off," is drawing power. This would include chargers such as for an electric toothbrush or shaver.

    Looking around for appliances that draw NO power when off, I find very few in my house. Here is an old-style radio with no lights or clock or remote -- when it's clicked off, it's really off... not many like that. Fans and lamps draw no power, your washer and dryer probably don't, but your stove and microwave probably do. My coffee-pot does; my coffer grinder does not. A can opener does not.

    Go around your house at night and note all the glowing LED's -- those appliances are drawing standby power, typically on the order of one watt, continuously.

    For reference, every watt of standby power will amount to a kilowatt-hour in 1000 hours, and that costs around $0.10. 40 watts of standby power will amount to about a kWh per day and cost you about $3/month.

  • 1 decade ago

    things like toasters do not draw any power when off.

    Some things do draw a few watts when off:

    1) things with a remote control (they have to listen for the power on signal)

    2) things with a clock, like VCRs, microwaves.

  • 1 decade ago

    ya dont worry about it its not worth unplugging them

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