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Energy, power, who cares?

By Matin Durrani

Here at Physics World HQ we’re more than happy with the concept of energy conservation.

So we have nothing against energy company E.ON’s attempt to get the public to reduce the amount of electricity they use by giving certain of their customers “energy monitors”.


These are small electronic gadgets that measure electricity consumption around the home in real time, allowing homeowners to keep close tabs on how much they are using.

But I was shocked to get an e-mail today from physicist Steve Bolter, alerting me to the fact that E.ON’s “Energy Fit” energy monitors indicate “Energy Now” measured in – wait for it – kilowatts.

If you don’t believe me, take a look at the picture on the right.

Even worse, click on the video above, which shows a smiling Kevin Bryant from E.ON showing the Fiddis family how the unit works. At about 3.27 minutes, you’ll see our Kev tell the unsuspecting Fiddises that “you are using 580 watts of energy at the moment”.

It’s enough to make you scream – particularly from a company that should know better.

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  1. Peter Morgan

    You’re picking at a common colloquial use of a technical language. I take it they’ve scripted this for energy instead of power because people aren’t very clear on the technical difference, just as people are not very clear on the technical difference between mass and weight. Colloquial uses of energy and of power are often indistinguishable. As far as I can tell, they’ve consistently talked about “using more energy” where we might prefer them to say “using more power”, but because this is not a formal language, so you can’t be sure that the meaning of the word “using” is the same in both cases. If you want to get into this, you would have to prove that the way they are using the word “using” precludes any possibility of a generous lay person thinking that the video makes any sense.
    Using technical language properly here could easily make the video opaque enough that the target audience would not try to understand it, which I think would be bad. Your choice. Try rescripting the video from beginning to end so that the language is technically correct at the same time as being clear and undaunting. We want to persuade not only scientists to use less power and/or less energy, right?
    In any case, the meter clearly measures power, which is labeled correctly in the upper portion of the display as Watts or KWatts. “Energy Now” even makes technical sense if we say that “Now” means “during the last second (or however long the ‘now’ is that the running power average is taken over)”. If you want to pick, the 7 day running average of the power could be said to be labeled incorrectly as KWHr, insofar as the number listed there is still a power, which ought to be listed as KWHr/week.
    Dear God, I’ve spent — wasted — more time picking at your pick than you spent on yours. Anyone want proof that scientists are crazy obsessive?

  2. The standard unit of measurement for energy consumed, the kWh, always seemed to me to be a potential source of confusion (wouldn’t Joule agree?), but I’m shocked and revolted that it resulted in bad labelling on meters that are supposed to help edumacate people in how much energy they use over time. OVER TIME! If this device actually does give an instantaneous power reading in kilowatts, it SHOULDN’T CALL IT ENERGY! Or if it really is measuring the energy used in the current second or the current minute, IT SHOULD GIVE PROPER UNITS!
    Sorry for yelling, but this got me rather charged up. Negatively.

  3. Glen Birbeck

    Even better, it should display DOLLARS SPENT per unit time. This we all understand. This would also bypass the brain and go directly to the gut.
    To highlight the present system and its total inability to inform people (of the money draining) I’ve used the analogy of an automobile which at the end of the month sent you a record of how fast you were going at various times during the preceeding 30 days! No wonder the loop is wide open.
    Real time display of power consumed in the home is long overdue but it should display dollars. People understand dollars.

  4. Great post. I’m always shocked at how the SI unit for energy, that most vital and unifying quantity of physics, has such a low profile!

  5. John Duffield

    This is just the tip of the iceberg, Matin. Take a look at that energy conservation: Now take a look at conservation of energy: Energy is always conserved. We don’t “consume” energy, we just spread it around a little. The capacity to do work describes what it does, not what it is. And most people, and not just ordinary people, don’t know what it is. It gets worse, because it’s like this for other things too. You might scream when an energy company confuses energy and power, but not as much as I do when I hear celebrity physicists talking about the possibility of time travel.

  6. Ross Anderson

    All they need to resolve this issue is to talk about KWatt Hours, which is commonly unit used in the utlitities sector for energy.

  7. myself

    wow, and when you americans will know that °F is … not SI? what about inch and mile?

  8. Thomas Goodey

    I think the screen on the meter is reasonably unobjectionable. It says “Energy now” and then a reading in kilowatts. Exactly maybe it should say “rate of energy use now”, but that is taken as a given. In any case, the only reason to show an actual energy reading in kWh would be if there was a wish to display the cumulative usage of energy over a period, and this is not that sort of meter. Given that there is limited space available on the display, I think that the electricity company can be forgiven.

  9. bsg

    Having just fitted a similar meter from another company, I think it is fit for purpose. ‘Energy Now’ is shorter to write than ‘ Current rate of electrical energy consumption’ and the meter also gives the cost equivalent for a specified period. And in my case, during set-up I was allowed to choose to use dollars or pounds, and had to provide a figure for the current charge made by my supplier for a KWh.


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