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Efficiency Math

During yet another one of those wonderful public service announcements on the radio I heard the claim that a compact fluorescent light bulb was typically “four to six times more efficient” than a traditional incandescent bulb. Leaving aside the issues of governments banning incandescents (why not tax electricity instead, and allow us the choice in how we conserve on use and CO2 emissions?) and leaving aside some people’s complaints that CFC wattages and lights are not comparable to incandescent ones I want to focus on the specific claim.

Suppose I take it as 100% gospel truth, and I have no reason to believe otherwise. I think this sort of thinking has us focus on a very small way of improving how much CO2 is emitted by our electricity production and/or how much energy we might conceivably save by various conservation strategies.

What the true measure of efficiency is, for me, is what percentage of the raw energy inputs end up being turned into useful work on the user end. Given that the modal electric outlet and light socket in the United States receives its electricity from coal-fired steam-turbine electricity generation plants, here is how I think of efficiency.

Coal has some amount of energy in it. In an idea world, 100% of that (potential) energy would be turned into work. However, we lose energy in every part of the electricity generation process. We lose energy during the coal combustion process as heat is lost up the exhaust pipes of the power plant. We lose energy (a lot of it) as the steam powers the turbine in the power plant. Most of the steam is lost as it escapes the teeth of the turbine. Then we lose energy as the turbine powers the dynamo via friction and heat losses. And then we lose energy in the transmission of the electric wires that run from the power plant to your outlet.

An optimistic estimate of the efficiency of this process is 36%. This assumes an 85% boiler efficiency, a 45% steam turbine efficiency and a 95% generator efficiency and no losses in transmission.  Suppose a typical incandescent bulb is only 5% efficient. Then in this case the efficiency of the entire system is only 1.8%.  Suppose a typical CFC bulb is five times more efficient, at say, 25%. As part of the closed system, then this would actually have a total efficiency of 9%. And yes, the CFC is still 5x more efficient than an incandescent bulb.

But, if we care about energy efficiency, consider that lighting makes up only a fraction of our energy use. So replacing 100% of incandescent bulbs with CFCs will not mean we save 5% of our energy and CO2 emissions, but a far small portion of it. Furthermore, think like a good economist. While it might make sense to replace all lights with CFCs to save up to x% of our energy loss, remember that energy is lost throughout the entire system. The only way “it makes sense” to use CFC’s is if to save a given amount of energy use and CO2 emissions this is the least costly way to do it. Is this possible? Sure. Is it likely? I don’t know. But think about steam-turbines for a minute. They lose over 55% of the energy applied to them. Just a small improvement in turbine efficiency would more than swamp efficiency gains from better light-bulbs. The right economic question is what cost we incur from doing each of these. Now, there is no reason to believe we cannot afford to make efficiency improvements throughout the entire system, as has happened anyway during the past 100 years.

Is there a better policy tool to “promote” the desired efficiency gains than mandating the use of a particular bulb? Of course there is. Let me discuss two points that are not often brought up in this discussion (many folks have done a fine job demolishing the sense of mandating CFC’s).

  1. Suppose we like the idea of government mandates, central planning and picking winners – totally ignoring the economics of input standards versus output standards. Does anyone ever stop to ask, “why lightbulbs?” Why not mandate that all customers install a particularly efficient electric heating system next year? Or how about mandating that all homeowners use a new kind of microwave oven or toaster? Yes, light bulbs make up a chunk of our electricity use, but it seems odd to pick an arbitrary component in an otherwise “target rich” home environment.  I am sure that Jeff Immelt has nothing to do with this.
  2. A simple “efficiency” tax at the front-end of the system would encourage innovation throughout the system and we’d likely end up with a “solution” that was the lowest cost way of getting the desired reductions. But why would we want to do that? Policymakers get it so wrong, so often, that one begins to think that they are afraid they would lose their job for getting policy right – thinking that they will solve themselves out of a job. But that is nuts. There are millions of things people can be working on, even policymakers. Zero-sum thinking is rarely productive.

6 Responses to “Efficiency Math”

  1. Trapper_John says:

    Certainly the solution smacks of crony capitalism, but I would guess that other parts of the system are already optimized for efficiency given current technology. Think about incentives through the system. For a power company, increases in efficiecy at the turbine or boiler go directly to the bottom line–the single most important value for a company. Given their profit incentives, increasing taxes on that end wouldn’t necessarily make a difference.

    As a light bulb consumer, however, I have multiple values that must be traded off when choosing a bulb: quality of light, quickness of brightening, joy from having a bulb that sparks conversations that would get me “uninvited from dinner parties”, price, and power consumption/efficiency. Given the low impact increased efficiency of light bulbs has on my power bill, it’s easy for me to forego the pennies/month just so the freaking bulb comes on NOW and AT FULL BRIGHTNESS when I flip a switch. The argument then goes that by short-circuiting my preference, small gains at the household level add up to make a big difference in CO2 emissions, fossil fuel consumption, etc. I.e., at a high level, there may be more available efficiency to be wrung from the back end of the process. And it lines GE’s pockets. Just a guess.

  2. Harry says:

    Great post, wintercow.

    PP&L gave me a hundred bucks for buying a new front-loading washer last summer. If one wants to, one can tell the washer to run at off-peak times. This happened without a bureaucrat holding a gun to someone’s head at PP&l, or more importantly to my head.

    Now if we all have to buy Volts or golf carts, I doubt PP&l will be sending me incentive money.

  3. Michael says:

    This is a bit off topic, but it is really interesting to see how many factors go into the lifespan of CFLs. One, you shouldn’t put them in a bathroom or anyplace that it won’t be on for 15 minutes at a time, frequent on/off cycles can reduce the lifespan by 85% according to the government (I think it was a DOE website). Two, don’t install them outside or in enclosed containers since they don’t like temperature changes. Three, make sure your bulb is correctly designed for the angle it is to be installed (i.e. some bulbs are not designed to hang upside-down). There are a few other things, but those are the main ones I can think of now. Another question could be the definition of “lifespan” since they’ll start to flash fairly early just like a normal fluorecent bulb. Is the end of life when it finally stops flashing or when I finally get annoyed enough to throw it away…I mean, toss in the apropriate container for mercury?

  4. Harry says:

    Michael, yes.

    There is some chance that congress will change this stupid rule, but remember GE retooled in China, and a plant in Winchester, Va, employing 400, shut its doors last year making light bulbs. Jeff Immelt won, Smith Barney won, and two out of three is not bad, right?

    Sometimes it is good to have bad law strictly enforced, as in the next time a voter’s reading light bulb goes out and he goes to the hardware store, and they tell him he has to spend $4.50 for this dumb thing, maybe he will get mad and ask questions.

  5. Rod says:

    I have a shower light above my bathtub that is designed for a 60-watt incandescent bulb. The new compact fluorescent bulbs will not fit inside the fixture, and even if it did, it would be exposed to steamy hot temperatures when I take a shower. It looks like I will have to replace the fixture with something that may or may not fit next to the floor joists of the attic in my 300-year-old house.

    All of this makes me ponder The Petition of the Candlemakers to Blot Out the Light of the Sun.

  6. Rod says:

    Another anecdote —

    When I was a township supervisor, the county made noises about “taking control” of all the trash in the county and shipping it perhaps to Upper Hanover, in the northernmost corner and as far from possible from Lower Merion. In defense, we supervisors investigated the possibility of building a municipal trash-to-steam facility in our industrial area, close enough to one potential industrial customer for the sale of the steam. Our aim was to solve our own trash disposal problems and the problems of six other adjacent municipalities and to be able to tell the county to shove the rest of the trash where the sun does not shine. At the time, the rate for co-generated electricity was only something like three cents per kilowatt hour (retail for PPL was about 4.5 cents) so the economics of the plant was a push as long as we could get enough trash to stoke the fire of the plant.

    We got the usual suspects lined up against us for polluting the air with unknown toxins, even though the proposed temperature for the plant’s incinerator was 1200 degrees, plenty of heat for reducing anything organic to CO2 and ash.

    We never did the project. The county decided not to take control of trash.

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