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Do you always unplug your phone charger?


By Hamish Johnston

Are you feeling environmentally smug because you don’t leave your mobile-phone charger plugged in all the time?

Well I’m afraid that the physicist David MacKay wants to knock the wind out of your micro-turbine.

He says that this act of greenness is pointless because it only cuts your daily consumption of energy by less than 0.01%. That, by the way, is enough energy to run a car for about one second.

“But every little counts”, you may be thinking. That’s true, but in his book Sustainable Energy — without the hot air , the Cambridge professor argues that folks should focus on making meaningful changes like turning the thermostat down or improving their home insulation. Indeed, he managed to cut his heating gas consumption by a factor of four by doing so.

“Obsessively switching off the phone-charger is like bailing out the Titanic with a teaspoon”, he quips.

And what about roof-top micro-turbines? “An utter waste of resources”, he says. Indeed, a typical micro-turbine would, on average, generate enough electricity to power four idle phone chargers — bailing out the Titanic with a tablespoon. However, the Sun is strong enough in the UK for heating water and a roof-top system could supply about half a family’s hot water needs, he says.

MacKay was on BBC Radio 4 today explaining why we should pay more attention to exactly how much energy we consume and how that energy could be generated — in cold , hard units of kilowatt hours per day (a horrible unit, I know). You can listen to the interview here.

Also interviewed was Rebecca Willis of the UK government’s Sustainable Development Commission, who didn’t seem too impressed with MacKay’s book.

She seemed to be saying that turning sustainability into a technical debate “turns people off”.

The BBC’s Tim Harford — an economist by training — accused the Commission of promoting “style over substance” in its literature. For example, it recommends micro-turbines so that people can feel “connected” to electricity generation. After reading MacKay’s book, Harford said he felt “betrayed” by the Commission.

You can read MacKay’s entire book online here

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  1. Turning off one phone charger may not make a substantial difference, but telling people not to bother is irresponsible surely?
    For the last 9 months or so I done or one or two minor things to reduce my household electricity consumption, including swapping my lightbulbs for low energy ones (hideous though they are), and turning off appliances (broadband router, laptop charger, television, aerial booster and hard-drive recorder) overnight.
    My household electricity consumption is one third to one half lower as a result, and that’s despite the fact that I now use a tumble drier, which I did not own previously.
    Some teaspoons are larger than others, it would seem!

  2. Francisco Taz

    I agree with the other commentator. Telling people to not bother unplugging, in this instance, a cell phone charger IS surely irresponsible. The metaphor of bailing out the Titanic with a teaspoon sounds clever but, it wouldn’t be just one teaspoon, now would it? If millions of people are unplugging those chargers every night then we’re talking about quite a bit of water being displaced, aren’t we? Or to put it in terms of the other metaphor used here: it would be many millions of seconds of energy to run that (hypothetical) car, wouldn’t it? Even a small amount, perhaps considered trivial initially, can become quite massive when raised a few powers of ten, no?

  3. Johann Rafelski

    Car-pooling once in 10 years has a greater impact. So does one extra week of school physics which allows to focus on valid recommendations: inflate car tires, close fridge doors faster, place hot water boilers on timers, equip lams/walls with mirrors, preheat car engines in winter, and do a 95 other things which are worth the effort, and yes, than phone chargers will probably come as item 101. Or, it could be 1001.

  4. Pauline, prof. MacKay isn’t telling us that we shouldn’t bother at all, but rather that we should focus on the areas that make a discernable difference rather than wasting our time, focus and resources that do not help or, in some cases, even make the situation worse.
    To exemplify: if for instance a paramedic that is treating the victim of a motor accident is trying to soothe minor bruises on the patient’s face while severed arteries are pumping out blood by the deciliters, then he’s clearly not helping the patient the right way.
    So if you have managed to cut your enegru consumption by 1/3, then that’s all find and dandy… for you. But not everyone can do this. However we could be cuttign energy production emissions by more than 90%(!) if we were to abolish coal plants for generating power and instead switched to nuclear power.
    Focus on the right things… not waste time with bits and pieces.

  5. Nick Cook

    Pauline, your right about some teaspoons being bigger than others but I think the main point David MacKay is making is not to kid yourself into thinking that turning of a phone charger makes any meaningful contribution to combating global warming, the environmentally warm feeling you get from this action is probably using more energy than your phone charger, although to be fair some older chargers are worse. The other point to consider is that electricity, or to be accurate the energy used to make it, probably accounts for less than 1/3 of most peoples energy use, unless you don’t travel and you don’t use gas for heating. So cutting electricity bills by 1/3 only represents about 10% reduction in carbon foot print, worth having but not as big in climate terms as many people might think.

  6. Thanks for your comments. Please don’t imagine that I advocate “not switching things off”. Do read the book. I strongly advocate switching things off, and being numerate about it. It’s available free on
    To the commentors who think that “if everyone does a tiny action, surely it adds up to a lot?” please read page 114
    which discusses the “if-everyone” multiplication machine. You can make any tiny gesture sound big if you multiply it by 60 million; but that doesn’t affect how tiny a fraction it is of the total. Focussing on minnows is BAD because it distracts attention from actions that would actually make a difference “if everyone did them”. Please Read the book instead of arguing against what you _imagine_ is in the book! David MacKay

  7. Eric

    Thank God someone is finally saying it. Alternate energy can’t be about pie in the sky nonsense that makes no meaningful change.
    Unplugging chargers is for all practical purposes useless, and worse… We delude ourselves into thinking that by engaging in this sort of silliness that the job is done and we can relax.
    Photovoltaic Cells are another solution that doesn’t actually solve anything.
    For the same amount of money it would take to power ONE house with Photovoltaic Panels (which only work when it’s sunny), you could equip a half a dozen house with Solar Hot Water and save the save the energy that would otherwise be used to heat over a thousand gallons of water per DAY.
    Far too often people reduce their views on energy to whatever sports team, sorry… POLITICAL party they belong to, and leave logic aside.
    One Team wants to ignore all energy except Carbon and Nuclear, while the Other Team thinks that Carbon and Nuclear can be replaced entirely and NEXT WEEK if only we elect the right talking head.
    The only way to solve the problems that face us is to see them as they ARE, not as we wish they were; and seeing them in the context that they ACTUALLY exist in, not the fantasy that we WISH we lived in.
    Take steps that MATTER. Like replacing every single bulb in your house with CFLs. Sealing the house properly with the sort of technology available at any Home Depot. Combine just TWO trips per week into ONE.
    On Fridays, I throw a nice big ice chest into my car, and shop at the supermarket that’s near my workplace. By doing that I save at LEAST one 20+ mile round trip per week. Minimum.
    That’s $1,000 miles per year, with almost no effort. 50 gallons of gasoline. A HALF TON of Carbon Dioxide.
    And I didn’t have to unplug a thing.

  8. Dan Hatton

    I’m going to suggest that “kilowatt hour per day” is not a “horrible” unit at all, but one that achieves something very important: it’s immediately clear to non-specialists that you’re talking about a rate per unit time. It’s not so easy to understand this from a more SI-compliant unit like “Watt”.

  9. Larry Brewer

    Hate to beat you up, but the thought that you would really be bailing out the titanic with “millions of teaspoons” is not quite accurate. You would be bailing out “millions of titanics” with “millions of teaspoons” and it is still utterly pointless. Or to put it another way… if everyone does just a little, then just a little will get done. In most cases you can’t even find a meter that can measure the current drawn by an idle cell phone charger.

  10. I’m going to suggest that “kilowatt hour per day” is not a “horrible” unit at all, but one that achieves something very important: it’s immediately clear to non-specialists that you’re talking about a rate per unit time. It’s not so easy to understand this from a more SI-compliant unit like “Watt”.
    JUST AS!


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