A new Dark Age descends upon us (revisited)

[This post is rewritten to reflect a clearer state of mind.]

The front-page editors of the local newspapers here in the Blue Ridge Mountains of western North Carolina had a tough time deciding on today's banner headline. Should it be the shootings at Virginia Tech or the damage wreaked by Monday's windstorm, which left much of this part of the state without electricity and destroyed what was left of the economically vital apple orchards not killed by last week's freezing temperatures. There's no way to spin any of it into the good news ledger, and I don't have access to my own computer files while the power's out, so instead I'm going to head off on a distracting tangent and ask, what's the difference between energy and power?

My wife and I have spent a good portion of the last two days on the telephone talking with -- or more frequently, waiting to talk with -- a real live human agent for Duke Energy, the utility that supplies the electrical current that runs most everything in our house, including the heat pump. To be fair, most wait times are in the single-digit minutes, and the agents are usually as helpful as they can be, which is to say however, not much. Information on when we could expect electrical service to be restored is not all that easy to come by, despite the fact we are supposedly living in a hyperconnected information age.

Most agents could not agreed on whether the power line repair crews knew about the tree that had taken out the neighborhood line, how long it might be before it was taken care of, how many other customers were similarly affected, or even whether we had previously reported a problem. But here's what I really want to know: Why did the company change its name from Duke Power to Duke Energy.

The corporate transformation, and the windfall for the stationery suppliers, took place in 1997, when Charlotte, N.C.-based Duke Power Co. took over Houston-based PanEnergy Corp. The name that the executives of the new corporate entity chose for themselves was Duke Energy. So what, then, is the difference between a "Power" company and an "Energy" company?

Energy (E) is another expression for work, which is a force (F) done across a distance (s). And, of course, a force is a mass (m) accelerated (a). Energy can be measured in joules

Power (P) is work (W) over time (t). It can be measured in watts, or joules per second.

Electrical power is typically defined as the amount of work done by an electrical current, or the rate at which electrical energy is transmitted (or supplied or consumed). This is why we pay for the electrons that whiz through our appliances in kilowatt-hours -- the watt is a measurement of instantaneous power, a figure that really doesn't mean anything to a consumer, whose needs rise and fall on a continuous basis. What we're really buying is power, not energy. I don't really care if those power lines, which are at the moment tangled in a tree lying across the street a few hundred meters from our house, can deliver a megawatt of power for a nanosecond. What I need is one or two kilowatts for several hours at a stretch.

So if the bottom line is really the bottom line, then when we get our bill each month, we're paying for joules per second multiplied by hours. Therefore it's

j * s-1 * h * 3600 s h-1 = 3600 j

So we're paying for joules, the work energy done each month by our appliances. And Duke "Energy" is correct.
There. I've said something nice about Duke Energy. Now, will they restore my electricity?


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Besides, everyone still asks, "Is the power back on yet?" And no one says "Do you still have energy?"

I sympathize. Besides, as I grow ... well, less young, I find that I sometimes give quite different answers to those two questions. :-)

By Scott Belyea (not verified) on 17 Apr 2007 #permalink

While it comes as little comfort now, the name change was due to the fact the prior to the merger with PanEnergy, Duke Power only supplied electricity to its regulated customer base in NC and SC. After the merger, they began dealing with a number of other facets of energy, including natural gas, natural gas processing (to create things like propane, butane, etc.), and gas trading. Since these activities typically don't fit into most peoples' definition of "power" (if your gas went out, would you say "Is the power back on yet?")and represented a significant addition to Duke's line of business, the name was changed to better reflect all of Duke's businesses.

By Michael McKinnon (not verified) on 18 Apr 2007 #permalink

You buy kilowatt-hours. That's a unit of energy. So, you buy energy. You don't pay more if you get it in a shorter period of time. Did i miss something in your argument?

Often, batteries' energy is measured in amp hours. This is so wrong. But, they expect that since the voltage is known (and it really isn't - it varies over the life of the charge), that you can do the math can come up with an energy value. But i'm sure that some energy company will note that since they mostly sell 117 volts RMS, they can call themselves Duke Amps.

Some communities have gone the extra kilometer and have underground power lines (which over time carry energy). These have various problems, but aren't subject to the weather so much.