Wattage

Josh sent me a nifty device for measuring the power consumption of various devices. This is something I’ve been meaning to do for some time: to see what drains power, and how much, and to see in particular what even drains power when it’s idle.

So I spent a couple of hours plugging it into various things and measuring how many watts they were pulling while running, and while not.

Although you often hear about appliances using energy while on standby, I found that for most, this was not the case. In most cases, they pulled zero watts while not running. But there were some exceptions, which I’ll note.

Pedestal fan: On setting one 33 W, setting two 38 W, setting three 45 W.

Kettle: 2289 W — whoa! So it’s important not to put more water in the kettle than you actually need, not just for the sake of speed, but also energy used.

Microwave oven: when running on high 1416 W.

Christmas tree lights: 28 W. It’s only a small tree, not one of those Christmas light extravaganzas you see some places. I don’t generally leave them turned on all the time anyway actually.

TV: Standby 19 W. On (including while muted) 80-120 W. It’s a 68cm CRT screen, and I’ve got it setup so that if left on standby for more than 30 minutes, turns itself completely off, which is good, as it’s apparent that leaving it on standby permanently would be a big waste of energy.

CD Player: 9 W, whether it was playing anything or not.

Amplifier: 16-17 W while on, whether it was silent, or playing radio or from a CD. Nothing measurable while on standby, despite the presence of a standby light.

XBox: Turned off 7 W. On but with no game running 55 W. Playing a game 55-64 W. Pah, 7 W when it’s switched off and doing nothing… bloody Microsoft, typically wasting resources.

MediaGate: On but stopped 11 W, playing 14 W.

DVD player: 9 W while on, whether it was playing or not.

Clothes dryer: Warm 1815 W, Hot 1900 W, During the cooling part of the cycle 75 W. I always knew these things used a lot of power, and this proves it… thankfully I don’t use it very much; the clothes lines (the main one, and another under-cover one for “high priority” items) works for most things.

Vaccuum cleaner: Min power 170 W, max power 1400 W.

Computer CPU: off 12 W, running Windows 75-90 W. Ridiculous… 12 W just to keep the clock going.

Computer screen: off 7 W, on 32 W.

Some things seemed to pull so little power as to be undetectable: the bedroom clock/radio, mobile phone charger, iPod dock and computer speakers all reported 0 W whether they were off, or on and blasting away/charging. I think the only electrical thing I can think of that I missed measuring is the washing machine.

There are some lessons here. Things like kettles and dryers should be used sparingly: don’t put more water in the kettle than is needed, and don’t use the dryer unless necessary. Most other appliances pale into insignificance compared to these.

And my plan is to re-arrange the powerboards to isolate those appliances that draw power while “off”… the computers and XBox (which after all is just a computer in a game machine’s body) in particular, so they can easily be switched off at the wall without affecting anything else.

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18 Replies to “Wattage”

  1. Hate to have a go at you, but you really need to do the maths to get anything usefull here. The biggest drawers are your kettle, microwave, clothes dryer, vaccuum, and probably washing machine. But they are off most of the time. (And I can’t think of anything you have missed.)
    Multiply them out by how long you have them on per week, do the same for standby. And it will probably be something completely different that stands out. If you calc the standby energy at on all the time, it may well be one of the bigger ones. (OK since you have given us the power, if you multiply it out and give us some of the others we could work out how long the TV and XBOX are on per week.)
    Then total them and calc how much CO2 you are producing from these. And compare that to how much you produce from your hot water, heating, stove and car. I suspect in your case, hot water and heating will dominate everything. And that there is little point in worrying about the others.
    Also, does the power meter give an instanteous reading, or does it average over an hour or so – this may affect the dryer.

  2. Things with electric heating elements in them use much more power than anything else. Heat from a gas flame is usually much cheaper. Here in the US. gas (natural or propane) is the most economical way to heat a home, heat water, cook, and dry cloths. Even heating a home with #2 fuel oil (common in the northeast US.) is cheaper than electric heat. Most Americans seldom line dry cloths and some private communities prohibit outdoor cloths lines as an eyesore. A washing machine uses little power. Most of the enegry consumed goes to heat the water. The same is true for a dishwasher. A dishwasher can save so much water over hand washing that the energy saved by not heating the extra water more than covers the power used by the timer, pump, and heating element in the machine itself!! I would guess that less than 1% of American homes have a water kettle. We use the stove or microwave when we need boiling water. We Americans don’t drink much tea or instant coffee so we have little need for them. Almost every American home has an electric drip coffeemaker. These use about 1500 watts but they are only on for a short time. American 120 volt appliances are limited to about 1500 watts (12.5 amps) as this is almost the maximum a 15 amp household circut can handle. Higher wattage appliances will have their own seperate 240 volt circut and circut breaker. We use 240 volts for electric stoves, central air conditioners, electric water heaters, central electric and baseboard heating, and electrically heated cloths dryers. Small l.e.d lights consume almost no power. This is why they didn’t register on the meter. An l.e.d. or indiglow nightlight costs about 3 cents per year to operate.

  3. I too would be interested in the figure for the ‘fridge. The very small difference between warm and hot with the clothes dryer is interesting. Altissima, most electric heaters have their consumption wattage on them, often 2400w on the highest setting.

  4. Thank you so much for posting this. Very interesting to see surprising results. Top call on filling kettle only with as much water as needed.

  5. Good point from Martin, I’ll do some more timed measurements, and will check the fridge.

    Randall, I’m not sure where it came from. Josh pointed out it may be of limited use after everything’s been measured, and I might like to pass it on, which makes sense, so I’ll look at doing that.

  6. A frost free fridge will consume more power than an old fashoned manual defrost fridge. The defrost cycle will have a different power meter reading than when the compressor is running. The defost cycle uses a heater to melt the frost off of the cooling coils in the freezer compartment. A small timer starts the cycle automatically a few times per day. There is also usually a small heater in the exterior strip between the fridge and freezer(the surface where the door gaskets contact)to prevent sweating. One might assume that when a fridge isn’t running it wouldn’t be using any power but this small heater and the defrost timer motor are always on and will show a meter reading even when the compressor and fans are off. Keep all of this in mind when measureing the fridge to get a true reading.

  7. I picked up one of these meters from Jaycar (http://www.jaycar.com.au/productView.asp?ID=MS6115&CATID=&keywords=power+meter&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=) when I picked it up they had tons of stock. The one that shocked me was my fisher & paykel washing machine uses 17 watts when “off” – I now have it on a switched powerboard so it can be turned off. The surprise for me was the home entertainment stuff – Amplifier, Sub Woofer, Set Top Box & VCR only used 7 watts when in standby – and considering I need the VCR & STB in standby to record stuff it’s not worth re-arranging the power (TV & DVD have proper power switches, so get turned off and use no power)

  8. Everything gets switched off at the powerpoint here and we’re slowly getting solar/dynamo powered products.
    We’ve halved our bills so far and they’re still dropping .

  9. My CD player uses 2 watts when running, but the DVD player uses 14 watts when on standby!

    Some equipment is just poorly designed, I think.

    My Mac Mini power supply draws 7 watts by itself, so the computer always uses 7 watts even when it’s off. When sleeping, the computer adds 2 watts to the 7 watts and when running it adds around 30-60 watts depending on what it’s doing.

    The killer is our 34 cm ‘second’ TV. It uses 21 watts on standby. Our 68 cm TV uses around 19 on standby and similar to yours when running. However it’s an LG so it’s short on features and can’t be programmed to switch itself completely off. Wish I had a Loewe…

    I found that our Fisher & Paykel washing machine uses 21 watts on standby too. But we just have to remember to turn it off when it’s finished. The good news is that even on its 1000 rpm spin it only uses about 300 watts.

  10. Standby mode requires power to be available to the standby circuitry.
    In standby mode, the circuitry downstream of the power-supply is generally off, but the power-supply isn’t off unless you physically unplug it from the mains socket.
    A fair proportion of that roughly 10W in standby mode is due to the inevidable inefficiencies of the power-supply itself caused by it’s transformers/coils, line-filters, power-conversion method.

  11. Yes but obviously the power supply in my CD player is able to keep itself alive and waiting for a remote control signal with only 2 watts. And a phone charger draws less than 1 watt. There is nothing stopping manufacturers from using that kind of circuitry to switch on the power to a larger circuit when required. That’s how they can all achieve a

  12. Sometimes we get lost with how much power 1 or 2 watts is.

    For instance 1 watt of audio is quite a loud noise (suitable to fill a small room from a portable radio), and that would draw maybe 2 or 3 watts.

    A two watt radio signal can be heard around the world given the right conditions.

    A torch globe capable of lighting a small area would be approximately 2 watts.

    Another appreciation of power was when riding a bicycle hooked up to a generator that could power several headlights. Producing several dozen watts (especially for any length of time) was really hard work.

  13. Hey Daniel. How about those compact fluorescent globes that are supposed to replace incandescent globes? Do they draw any power when the light is turned off, but with the plug left switched on at the wall? Just wondering because I know they have a little circuit board in the base of the globe, and was curious if it still draws power when the light is turned off.

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